Here is the full list of all 53 The Morrigan achievements.
Complete the Tutorial
Complete Beginnings on easy difficulty
Complete Beginnings on medium difficulty
Complete Beginnings on hard difficulty
Complete The Tomb on easy difficulty
Complete The Tomb on medium difficulty
Complete The Tomb on hard difficulty
Complete The Church on easy difficulty
Complete The Church on medium difficulty
Complete The Church on hard difficulty
Complete The Garden on easy difficulty
Complete The Garden on medium difficulty
Complete The Garden on hard difficulty
Complete The Bridge on easy difficulty
Complete The Bridge on medium difficulty
Complete The Bridge on hard difficulty
Complete The Rampart on easy difficulty
Complete The Rampart on medium difficulty
Complete The Rampart on hard difficulty
Complete The Gates on easy difficulty
Complete The Gates on medium difficulty
Complete The Gates on hard difficulty
Complete The Tunnels on easy difficulty
Complete The Tunnels on medium difficulty
Complete The Tunnels on hard difficulty
Complete The Ruins on easy difficulty
Complete The Ruins on medium difficulty
Complete The Ruins on hard difficulty
Complete The Ascent on easy difficulty
Complete The Ascent on medium difficulty
Complete The Ascent on hard difficulty
Complete The City on easy difficulty
Complete The City on medium difficulty
Complete The City on hard difficulty
Complete The Dungeon on easy difficulty
Complete The Dungeon on medium difficulty
Complete The Dungeon on hard difficulty
Complete The Escape on easy difficulty
Complete The Escape on medium difficulty
Complete The Escape on hard difficulty
Rescue the Queen
Complete the game
Reach wave 3 in the arena
Reach wave 5 in the arena
Reach wave 8 in the arena
Reach wave 13 in the arena
Reach wave 18 in the arena
Reach wave 25 in the arena
Reach wave 3 in the temple
Reach wave 5 in the temple
Reach wave 8 in the temple
Reach wave 13 in the temple
Reach wave 18 in the temple