User blog comment:Hibridragon/Mimic(s)/@comment-24277289-20150123150734

Every Wednesday, there is a Vortex Event where the mimics can be found. Occassionally, Mimics will drop from chests during Quests as well. From Palymna onwards, you can pick up Bat and Dragon Mimics quite frequently from chests. If you want Metal Mimics, you will have to do the first two Wednesday dungeons as they have a chance to appear there (they do not appear on the third dungeon) or you could evolve a Bat Mimic with a Metal God, King, and Ghost.

Hope this helps!