View all the monotype teams here: https://pastebin.com/S419KvS5
 
Pokemon Battle Tower Monotype team challenge
ICE team
Version: 2.1
 
J (Jynx) @ Petaya Berry
Ability: Oblivious
Level: 50  
EVs: 4 HP / 252 SpA / 252 Spe
Timid nature  
IVs: 31 HP / 0 Atk / 31 Def / 31 SpA / 31 SpD / 31 Spe  
- Ice Beam
- Psychic
- Calm Mind
- Substitute

R (Regice) @ Leftovers
Ability: Clear Body
Level: 50
EVs: 252 HP / 244 Atk / 4 Def / 4 SpD / 4 Spe
Impish nature  
IVs: 31 HP / 31 Atk / 31 Def / 31 SpA / 31 SpD / 31 Spe  
- Thunderbolt
- Counter
- Protect
- Explosion
 
W (Walrein) @ Lum Berry
Ability: Thick Fat
Level: 50
EVs: 12 HP / 252 SpA / 244 Spe
Modest nature  
IVs: 31 HP / 2 Atk / 31 Def / 30 SpA / 31 SpD / 31 Spe 
- Surf
- Ice Beam
- Hidden Power [Grass]
- Sheer Cold
 
Notes:
- Jynx is actually really good -- it beats nearly every Special attacker thanks to Calm Mind, and STAB Ice Beam and Psychic OHKO many physical threats (Rhydon, Golem, Blaziken, Heracross, etc.). Substitute can block status moves, activate Petaya Berry, and give Jynx much-needed protection later in the battle.
- Walrein switches into Fire types comfortably thanks to Thick Fat, and it OHKOs them with STAB Surf. It also OHKOs many dangerous Rock types. Sheer Cold is its best bet against Special walls -- the odds are actually in your favor to hit one before you die, especially since Sheer Cold's accuracy is unaffected by Double Team.
- Regice's moveset looks strange, but the moves and EV spread work well together. Thunderbolt beats Water types, Counter beats physical attackers, Protect + Leftovers gives it extra staying power and potentially another Counter, and Explosion nukes special tanks that wall Jynx and Walrein. The Attack EVs are very efficient for netting Explosion OHKOs since Regice's base Attack is so low. The 4 Defense EVs give Regice a higher chance of surviving Metagross' Meteor Mash, and the 4 Speed EVs allow it to outspeed uninvested base 50s.