Mementos

Mementos can be found through the game In Celebration of Violence. Mementos can be found in crystals. You can break crystals for experience and glass, or pay the listed cost to buy the memento. If you can't make out which is what, bring up the action menu and use Inspect on them.

Common mementos cost 25 exp, Uncommon cost 50 and Rare cost 100. You will also find un-inspectable mementos for 35.