Here is the full list of all 29 Magi's Dream achievements.
Reach wave 50
Reach wave 25
Unlock all maps
Replace an inventory item
Defeat the Ghoul King
Defeat the Master Guardian
Defeat the Harvester
Defeat the Megalodon Revenant
Defeat Hadrian's Ghost
Escape from the dream
Hold 1 million coins
Complete a favour for any of the Magi
Complete all favours for Odin
Complete all favours for Atlas
Complete all favours for Boreas
Complete all favours for Ifrit
Complete all favours for Solomon
Complete all favours for Tian
Complete all favours for Merlin
Complete all favours for Lucifer
Complete all favours for Vindex Ahti
Complete all favours for Sunyata
Equip a challenge modifier
Increase any stat to level 5
Increase any stat to level 10
Activate the Pyromancer's ultimate ability
Activate the Cryomancer's ultimate ability
Upgrade any item to level 20
Obtain all Stories