Prototype

THE UNDERTERROR

HIT POINTS
Hit Dice: 1d10 per Underterror level
Hit Points at 1st Level: 10 + your Constitution modifier
Hit Points at Higher Levels: 1d10 (or 6) + your Constitution modifier per Underterror level after 1st.

PROFICENCIES
Armor: Light armor
Weapons: Simple weapons, martial weapons
Tools: Choose one type of artisan’s tools
Saving Throws: Constitution, Wisdom
Skills: Choose two from Arcana, Deception, Intimidation, Perception, Sleight of Hand, Stealth, Survival.

EQUIPMENT
-Leather armor
-One simple or martial weapon
-(a) a dungeoneer’s pack or (b) an explorer’s pack.

NATURAL WEAPONS
Beginning at 1st level you gain the ability to reshape your body to create natural weapons.
-During a long rest you can create a number of natural weapons up to your proficency bonus. Choose what type of damage each one does: piercing, slashing or bludgeoning. The damage of yor natural weapons starts at 1d4, increasing to 1d6 at 5th level, 1d8 at 11th and 1d10 at 16th.
-You're always considered proficent with your natural weapons, which all have the Light and Finesse properties. You can use your Constitution modifier instead of Strength or Dexterity when attacking with them.
-You can draw and sheathe all your natural weapons at will, without using an action, and have as many drawn at the same time as you can create. The first weapon you draw mutates one of your arms, making it difficult but not impossible to wield and hold objects, but successive ones can sprout from anywhere on your body.
-Even for an alien mind it's difficult to coordinate more than two limbs in the chaos of combat, so your natural weapons follow all the normal rules for dual wielding.
-You have a pool of Mutation Points equal to half your level + Con mod, maximum 10. Every time you create weapons you can use them to assign various extra traits to them, or reassign already allocated points. See below for a list of available mutations, with their points cost in parentheses.
-Some effects tied to your natural weapons require creatures to pass a saving throw. The DC is 8 + Proficency + Con mod.

MUTATED MOVEMENT
Beginning at 2nd level your speed is increased by 10 feet. At 9th level you also gain half your walking speed as climbing and swimming speed, or increase them by 10 if you already have one.

DARKVISION
Beginning at 2nd level you gain darkvision up to 60ft. If you already have darkvision its range is increased by 60ft.

ARCHETYPE
(WIP, choice at 3rd level, additional features at 6th, 11th and 17th)

ABILITY SCORE IMPROVEMENT
(Same as every other class)

EXTRA ATTACK
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn. This number of
attacks increases to 3 at 13th level.

BODY MUTATIONS
Beginning at 5th level you can use your mutation points to gain passive bonuses instead of improving your natural weapons (see below).

IMPROVED WEAPON MUTATIONS
Beginning at 7th level you gain access to a greater array of mutations for your weapons (see below).

EVASION
Beginning at 9th level, you can nimbly dodge out of the way of certain area effects, such as a red dragon’s fiery breath or devastating spells due to your enhanced reflexes. When you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail.

EVER-SHIFTING
Beginning at 10th level you have advantage on saving throws against being restrained or paralyzed, and on checks to overcome those conditions or avoid being grappled. Additionally when you're grappled or restrained or paralyzed you can use an action on your turn to end the condition.

TINDALOSIAN STRIDE
Beginning at 12th level you can, once per short rest, use an action to move up to twice your speed. During this movement you don't trigger opportunity attacks, can move at full speed on any surface regardless of orientation and ability to bear weight, and are immune to damage.

IT WILL NOT DIE
(Alternate name: Impervious Flesh)
Beginning at 14th level, when an attacker hits you with an attack, you can use your reaction to negate the attack's damage against you.

GRASP THE TRUE FORM
Beginning at 15th level you gain truesight with a range of 20ft, and can sense magic within 60ft as if under the effect of the spell Detect Magic.

INDESCRIBABLE
Beginning at 18th level the first attack against you by each creature within 15ft each round has disadvantage.

LETHAL MUTATIONS
Beginning at 19th level, when you attack with a natural weapon and roll the highest possible number on the damage die, roll that die again and add it to the damage. You can keep rerolling until you roll anything less than the highest number. If you make use of an effect that maximizes the damage of your natural weapon you can roll the damage die once and add it.

TOO HORRIBLE TO DIE
Beginning at 20th level you are immune to critical hits. This includes both the extra damage dice and any special effect that would activate on a critical hit. You can no longer be incapacitated or killed due to dismemberment or decapitation; if one of your body parts is severed but is still intact you can hold it to the stump and the two instantly knit together. Lastly, once per short rest if you would die you're only knocked unconscious for 1 minute instead.
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BASIC WEAPON MUTATIONS (Available from 1st level)
Firmly Attached (1 point): Whenever an attack, spell or effect would prompt you to “drop” your natural weapon, sever it or otherwise affect it negatively, you gain advantage on the saving throw to resist it.
Heavy (2): The weapon's damage die is increased by one size (d4>d6>d8>d10>d12) but it can no longer be used to make extra attacks as a bonus action.
Protean (1): You can choose for the weapon to do bludgeoning, piercing or slashing damage each time you attack.
Reach (2): The weapon gains 5ft extra reach. Melee only.
Ranged & Loading (2): This weapon is treated as a ranged weapon with range (80/320) and the Loading property. It has an internal reserve of 20 ammo that is replenished on a short rest.
Shield (2 or 4): While this weapon is drawn it grants you +2 AC. For 2 points it must be manifested on an arm, for 4 it can be anywhere on your body. You can only ever gain extra AC from one shield.
Sinister (1): When you make an "off-hand" attack with this weapon as a bonus action you may add your ability modifier to the damage roll.
Spiked (1): While drawn, this weapon automatically deals its damage every turn to enemies you are grappling or who are grappling you. It also deals its damage on a successful Shove.
Stinger (1): On a critical hit the target must pass a Con save or be Poisoned for 1 minute.
Thrown (1): This weapon is treated as a throwing weapon with range (10/60). After throwing it it's not lost, but is considered to have a reservoir of 10 ammo that is replenished on a short rest.

ADVANCED WEAPON MUTATIONS (Available from 7th level)
Brutal (1 or 2): This weapon scores a critical hit on a roll of 19+ for 1 point, or 18+ for 2 points.
Devastating (2): This weapon ignores damage resistance (but not immunity).
Energy Mutation (1): Choose one of the following damage types for the weapon instead of the standard ones: acid, cold, fire, lightning, poison or thunder.
Flailing (1): This weapon has advantage on opportunity attack rolls.
Internal Quiver (1): Thrown or ranged only. Your internal reservoir of ammo for this weapon is increased to 120.
Ram (2): If you hit with this weapon, you can spend a bonus action to force the target to pass a Strength save or be knocked prone.
Ranged (3): This weapon is treated as a ranged weapon with range (80/320).
Scything (2): Melee only. As an action you can make a single attack against all enemies within weapon range. If you do you cannot use your bonus action to make an off-hand attack.
Volatile (2): Ranged only. If this attack hits, all other creatures within 5 ft of the target must pass a Dexterity save or suffer half the weapon's rolled damage.

BODY MUTATIONS (Available from 5th level)
Aquatic Adaption (1 or 2): You can breathe water. For 1 point you gain half your speed as swimming speed, for 2 your full speed. If you already have a swimming speed 1 point lets you increase it by half instead.
Arachnid Adaption (1 or 2):  You have advantage on saving throws against being pushed and knocked prone. For 1 point you gain half your speed as climbing speed, for 2 your full speed. If you already have a climbing speed 1 point lets you increase it by half instead.
Aerial Adaptation (3 or 4):  For 3 points you gain half your speed as flying speed, for 4 your full speed.
Enhanced Constitution (1): You have advantage on Constitution checks and saving throws and you gain temporary hit points equal to your level every time you complete a short or long rest.
Enhanced Dexterity (1): You have advantage on Dexterity checks and proficency on Dexterity saving throws, and all your movement speeds are increased by 5ft.
Enhanced Strength (1): You have advantage on Strength checks and proficency on Strength saving throws, and all your melee or natural weapon attacks deal +1 damage.
Anti-toxin (1): You have advantage on saving throws vs. poison. As a reaction you can take one level of fatigue to end all poison effects on you.
Adrenal Booster (1): You have advantage on saving throws vs. fear. As a reaction you can take one level of fatigue to end all fear effects on you.
Hormone Booster (1): You have advantage on saving throws vs. charm. As a reaction you can take one level of fatigue to end all charm effects on you.
Immune System Booster (1): You have advantage on saving throws vs. diseases. If you gain one or more levels of fatigue you can ignore their effects for a number of hours up to your Con mod, but at the end of the effect you suffer 2 additional levels of fatigue.
Nictitating Membrane (1 or 3): For 1 point you have advantage on saving throws vs. gaze attacks, for 3 points you're immune to them.
Natural Armor (2 or 4): For 2 points when wearing no armor your AC is 10 + Dex mod + Con mod. For 4 points you can add 2 to this number.
Natural Resistance (2 to 6 OR 5): For every 2 points you gain resistance to one element from the following list: acid, cold, fire, lightning, poison or thunder. Alternatively for 5 points you gain immunity to one element from the list.
-Noxious Breath (1): You know the cantrip Poison Spray or Acid Splash, using Con as your spellcasting stat.
Tremor Sense (2 or 4): You gain tremorsense up to 30ft. For 2 points this ability only works while you stand still.
Upper World Adaption (1): You lose the Light Sensitivity trait if you have it.
Unspeakable Feedback (2): Anyone trying to contact you via telepathy, read your mind or similarly touch your psyche must immediately make a Wisdom saving throw or the attempt fails and they take your Wis modifier times 1d6 psychic damage.
Obscene Vitality (3): You are resistant to necrotic damage and your max HP can't be reduced.
Acid Blood (2): A creature within 5ft that damages you with an attack immediately takes your class level in acid damage.
-Chameleontic (3): You can cast Invisibility on yourself at will, with the duration reduced to 1 round. Once you use this feature you can't use it again for 1d4+1 rounds. Outside of combat, you can cast proper Invisibility on yourself once per short rest.

UNDERTERROR ARCHETYPES

ARCHETYPE - THE MONSTROSITY
SIGNATURE MUTATION
When you chose this archetype at 3rd level, chose one weapon mutation to be your signature. Its point cost is reduced by 1, to a minimum of 1. Every 4 levels after that you can pick an additional weapon or body mutation to be signature and change any previous pick for another one. At 19th level, when you take your final pick, the costs are reduced by 2 to a minimum of 0.
POWERFUL MUTATIONS
Starting at 6th level, all your natural weapons count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage, and gain a +1 bonus to attack and damage rolls. The bonus is increased to +2 at 10th level and +3 at 14th.
FLEXIBLE MUTATIONS
At 11th level your maximum mutation points are increased by 4 and you can rassign up to half of them when you finish a short rest.
MUTATION SURGE
At 17th level you gain the ability to wash over with a horrifyng surge of change as an action. For 2 turns afterwards you are resistant to all damage types and any opponent who wishes to get closer to you must pass a Wisdom saving throw against your natural weapon DC or be unable to do so. After using this ability you must finish a short or long rest before using it again.

ARCHETYPE - THE SLASHER
IMPOSSIBLE FLEXIBILITY
When you chose this archetype at 3rd level you gain proficency in Stealth if you didn't have it already, and you add double your proficency bonus to Stealth checks. You can also fit into any space large enough for a creature one size category smaller without squeezing, or in any space as small as 1 inch wide while squeezing.
WITH MY LITTLE EYE
Also at 6th level you gain the ability to detach one of your body parts as a semi-independent creature and use it to keep an eye on your surroundings. This works like the spell Arcane Eye but with the following exceptions: It can be cast at will; It doesn't require any components; The sensor possesses any special sense the caster possesses, like tremorsense or darkvision; it's not invisible but just very hard to spot, requiring a DC 25 Investigation roll under normal circumstances; it cannot fly but can cling and crawl on any solid surface regardless of orientation.
BEHIND YOU!
At 11th level the Chameleontic Skin mutation becomes free. You can upgrade it by assigning 3 mutation points, allowing you to cast Invisibility on yourself at will with no limitations and granting advantage on Stealth checks. Additionally, creatures cannot detect you with Blindsense, and you are invisible to Tremorsense unless within 20ft of the user.
CURSE OF THE RED SHIRT
At 17th level, attacks you make against creatures whose hit dice or class level are lower than your Underterror level by 5 or more hit automatically and kill the target outright (and very gorily). Additionally, when you reduce a creature to 0 HP with an attack you can use Tindalosian Stride again as if you had complete a short rest.

ARCHETYPE - THE AWAKENED
SPELLCASTING
-Cantrips: When you choose this archetype at 3rd level you learn 2 cantrips from the Warlock spell list.
-Spells Known of 1st level and Higher: At 3rd level, you know 1 spell of your choice between Dissonant Whispers and Tasha's Hideous Laughter. As you gain levels you can learn additional spells of your choice from the Warlock spell list or from the Great Old One Warlock patron bonus spells list. When you gain a level in this class, you can choose one of the spells you know and replace it with another spell from the same selection, which also must be of a level for which you have spell slots.
-Spellcasting Ability: Wisdom.
-Spell Slots Recovery: At the end of a short or long rest.

Level |  Cantrips Known  |  Spells Known  |  Spell Slots  |  Slot Level
 3            2                 1                1              1st
 4            2                 2                2              1st
 5            2                 2                2              2nd
 6            2                 3                2              2nd
 7            2                 3				 2              2nd
 8            2                 4                2              2nd
 9            2                 4                2              3rd
10            3                 5                2              3rd
11            3                 5                2              3rd
12            3                 6                2              3rd
13            3                 6                3              4th
14            3                 7                3              4th
15            4                 7                3              4th
16            4                 8                3				4th
17            4                 8                3				4th
18            4                 9                3				4th
19            4                 9                3				4th
20            4                10                4				4th

ALIEN MIND
At 3rd level you have advantage on Wisdom saving throws. Additionally the Unspeakable Feedback mutation becomes free for you, and you may upgrade it by assigning 2 mutation points, extending its effect to attempts to charm you and causing telepathy and mind reading effects to fail even if the victim passes the saving throw.
YOU CANNOT GRASP THE TRUE FORM OF THIS ATTACK
At 6th level, whenever you have the Natural Resistance mutation active you also gain resistance or immunity to psychic damage in addition to whatever damage type you're resistant or immune to. When your attacks or spell deal damage that isn't bludgeoning, piercing or slashing you can have them do psychic damage instead of the normal damage type.
I WILL SHOW YOU THEM
At 11th level whenever you deal psychic damage to a creature they have disadvantage on saving throws caused by your spells and abilities until the end of your next turn.
EPIPHANY
At 17th level the veil has been shorn. Your type becomes Aberration instead of Humanoid if it wasn't already. Aberrations and Outsiders from the Far Realm see you as kin; they will not attack first unless they have a reason, and even if they're hostile when encountered they will always attemp to "negotiate" before attacking. Finally, you can always take 15 on Arcana, History, Religion and Nature checks regarding knowledge of the planes, the Far Realms, the outer dark and similarly obscure and forbidden knowledge.