As of most recent patch Phaestus theme dissapeared from extras unlockable menu completely
Went to check what achievements were needed and its entry had dissapeared. All other themes were present however.
Customer support service by UserEcho
This is intended due to the phaestus theme bound to the hidden achievements, sadly we kinda messed up the surprise by unlocking everything from the start :P
im sorry for the inconvenience, for both, the tease and the mystery behind the hidden achievements ... :D
No problem! I was just worried it had been removed for some reason :) Thanks for the confirmation!