Here is the full list of all 15 Holy Towers achievements.
Holy warrior
Patron of the сider brewers
Highlander
Thank you for being alive
Greed is not a sin
Passed 5 additional levels
Torturer of the flesh
Passed 50 additional levels
Used Holy rock
Collected all the daily bonus
Opened additional slots for towers at 15 levels
Used the Chaplain on one of the levels
Used Drunkel on one of the levels
Used Borgia on one of the levels
Used Erelim on one of the levels