Randorosu - CCGn3 RMT

Yo, it's your boi Landorus AKA Randorosu AKA Big Dawg AKA Banned from OU. Aight anyway, this is the ground team I created to take on the 3rd Ground Core Challenge:

Landorus (M) @ Life Orb
Ability: Sheer Force
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Earth Power
- Gravity
- Psychic
- Sludge Wave

Gliscor @ Toxic Orb
Ability: Poison Heal
EVs: 252 HP / 56 Def / 200 Spe
Impish Nature
- Fling
- Acrobatics
- Taunt
- Roost

Excadrill @ Choice Band
Ability: Sand Rush
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Iron Head
- Earthquake
- Rock Slide
- Rapid Spin

Gastrodon @ Leftovers
Ability: Storm Drain
EVs: 252 HP / 4 Atk / 252 Def
Relaxed Nature
- Recover
- Scald
- Earthquake
- Toxic

Steelix @ Steelixite
Ability: Sturdy
EVs: 248 HP / 60 Def / 200 SpD
Impish Nature
- Earthquake
- Heavy Slam
- Rest
- Sleep Talk

Hippowdon @ Smooth Rock
Ability: Sand Stream
EVs: 248 HP / 148 Def / 112 SpD
Impish Nature
- Slack Off
- Stealth Rock
- Earthquake
- Whirlwind

Steelix-Mega is a pretty underrated mega for ground, and rightfully so. It is rather slow and has decent attack power but not enough to make it super scary. It does have massive defensive bulk but a little bit lacking in HP, which made things quite difficult for me. I used Mega Steelix to be my wall for ice and a couple grass type pokemon. RestTalk for longevity of course and Heavy Slam + Earthquake for nice STAB especially in the sand. Obviously, this give me a weakness to Ground, Fighting and Fire. To cover 2/3 of those weaknesses, I thought Gliscor would be a good addition to the team. Fling is for Mega Sableye's that can be a threat to the team, Taunt for Pokemons like Mew, Chansey and Skarmory so they can be worn down by my other mons and Acro for Grass and Fighting Pokemon who normal beat Gliscor or threaten Ground Monos. Steelix still had to be covered for it's Fire weakness, so I added Gastrodon. Gastrodon is one of the main 2 Ground Pokemon which are usually a staple on Ground Monos being able to absorb water moves. Along with the absorption, the resistance to Fire moves really helps Steelix out and adds somewhat of a counter for Keldeo. Earthquake on Gastrodon is mainly for SubCM Keldeos so I can guarantee breaking the substitute barring a weird Defensive Set with the other moves being self-explanatory. On paper, I have covered all my weaknesses typing wise, now serious attack power needed to be added. Landorus and Excadrill are major Pokemon on Ground Monos because they threaten a lot of teams especially when paired together. Landorus is given Gravity for another answer to Skarmory along with other ungrounded mons and, with Sand Support from Hippowdon, Excadrill with a Choice Band can 2HKO a majority of the meta. Psychic as another check for Fighting Monos and Sludge Wave for Pokemon like Un-boosted Azumarill who cannot OHKO Landorus at full HP with Aqua Jet. As stated before Banded Excadrill 2HKO's a majority of the meta with Earthquake and Iron Head with pretty much the other moves as filler. X-Scissor could replace Rock Slide or Rapid Spin for a tiny bit more damage against Psychic Pokemon but those were the moves I tried to go for. Hippowdon explains itself.

Threats

Water Monos - These are extremely threaten as expecially if they have Swift Swim support. Keldeo + Azumarill are really dangerous and requires me to keep Gastrodon healthy and to wear them down with Toxic + Sand. Gastro now longer becomes viable if the Azumarill has Belly Drum or Choice Band. Alomomola is also a threat but can also be worn down similarly. Sand Rush Excadrill also checks Keldeo after Sandstorm Damage.

Grass Monos - Breloom often threatens my teams with my only counter being Gliscor. Granted Gliscor handles it pretty well, it's a threat none-the-less. Serperior can tear through my team and is an automatic GG if Hippowdon dies and Steelix is weakened and my only check being Excadrill. Ferrothorn also sponges all hits I can dish out relatively well while also being able to wear down everything with Leech Seed. Steelix can potentially stall it out but leave you vulnerable to other Pokes on Grass Monos., adding Focus Blast on Landorus makes it much easier to take on assuming you hit it.

Mega Charizard Y - Though Ground does have an advantage typing wise, this man threatens most if not all Ground Teams. Mega Charizard Y effectively destroys my entire team and requires me to play my Hippowdon on point. If the player is inexperienced and Solarbeam's first turn my Hippowdon can eat it up and dish out a Stone Edge making Fire much easier. Landorus can deal with it after a Gravity but has to somehow get it off in the first place. Excadrill can also help if the person believes Sun would cancel out the Sand Rush Speed Boost first turn.

Kyurem-B - 2HKO's my entire team and is rather bulky. Mega Steelix can eat up a hit depending on the set and Excadrill is required to come in and OHKO it in most cases which gives a Free Switch to Rocky Helmet Chomp which weakens Excadrill and forces it out.

Obviously they're many other threats but I cannot list them all; those are just a few. You'll find the other when you battle with the team.

Replays:

https://replay.pokemonshowdown.com/monotype-235823224 - Ground vs Ground
https://replay.pokemonshowdown.com/monotype-235294693 - Lol
https://replay.pokemonshowdown.com/monotype-235288744 - Ground vs Water
https://replay.pokemonshowdown.com/monotype-235284891 - Ground vs Fighting