Calamity mob ideas

Hallowed Knight - A rare enemy that spawns in the Hallow after one Mech Boss has been defeated. It's a humanoid mob wearing full Hallowed Armour, riding a Unicorn, and wielding a Gungnir.
The Hallowed Knight will spend most of its time charging at the player, like a typical Unicorn, however it has much more jump height than normal, and a vastly extended hitbox due to its Gungnir.
The Knight has a chance to drop Hallowed Bars, and can serve as an alternate method of collecting the bars instead of forcing the player into grinding the Mechanical Bosses.

War Elephant
A large elephant that wanders the desert upon the Moon Lord's defeat, it has loads of HP (but not enough for it to take ages to kill), moves very slowly, doesn't jump high if at all, and has 100% knockback resist.
Occasionally, it may stop for a second and perform a charging attack, throwing itself forwards and dealing extra damage to the player.
Available in the post-Moon Lord desert, this mob is inspired by the War Elephant of Age of Empires fame. In Age of Empires II, it is the unique unit of the Persian civilization, and is well known for its immense strength, lack of speed, and weakness to conversion. I hate monks so damn much.
The reason why I want this guy added is because the post-Moon Lord world is very lacking in regular enemies, containing only Profaned monsters, and creatures in the Abyss, and the rest of the world needs some love.
Drop: Heavy Horn
It may drop a horn that calls forth an elephant for the player to ride on. This Elephant mount has the speed of a Basilisk mount, but it has extra damage dealt when entering its "charging" stage. It also has a high fall speed, roughly the same as a Slime mount, so as to not render the Pyukumuku mount obsolete, but when the Elephant lands on a tile, it will create a shockwave that spreads out to the sides, dealing damage to enemies the waves connect with.

Lihzahrd Karambit
A post-Moon Lord enemy that spawns in the surface Jungle, it fights like a typical fighter, similar to its counterparts in the Temple, however, this one has a trick up its sleeve:
The Lihzahrd Karambit's presence causes identical Lihzahrd Karambits to spawn around the player, but only a certain amount can appear, and the "clones" cannot summon extras, so the player would be forced to find the "real" Karambit and slay it before they get overwhelmed by numbers.
Like the War Elephant suggestion above, the Lihzahrd Karambit is also inspired by a unit from Age of Empires II, this time the Karambit Warrior - unique unit of the Malay civilization in the Rise of the Rajas expansion. The Karambit Warrior has very low stats compared to other units available in its tier, but they make up for this fact by having a very low resource cost, fast training time, and the fact that they are the only unit in AoE II to take up half a population slot. I tried to incorporate this by having the Lihzarhd Karambit "summon" other Karambits to its side, so as to make the player seem like they're being swarmed.
I'm also interested in the idea of Lihzarhds appearing outside the Temple upon the Golem's defeat. The player stormed their home and destroyed their greatest guardian, thus leaving them vulnerable, but also letting them step outside and explore their world, of which they didn't have the chance to do so.