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