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