Here is the full list of all 27 Rooks Keep achievements.
Win 200 matches
Kill 1000 enemies
Kill 10 enemies using Bash
Win in every arena map
Win a match as every character (arena modes)
Draw first blood
Win in every Chess map
Win 20 matches
Win each game-mode
Defeat the attacker in Combat Chess
Beat the AI at Classic Chess
Turn your pawn into a queen in chess
Eliminate all teams without changing sides (Conversion)
Defeat a Warlord
Become the Warlord
Defeat an upgraded piece (5 skills at least) without your own upgrades
Kill an enemy with your ability
Win a round without losing a life (LMS, TLMS)
Win a Team-Match
Kill 10 team members
Win a match with 5 mutators running
Kill 10 characters in one life with the Damage
Fully purchase all skills
Win a match
Kill 25 enemies without dying
Kill 10 enemies without dying
Upgrade your character 10 times in the same life