Crystals

(This is a stub) Crystals are only obtainable in The other kind of arena.

They are bright pink in color and look kind of like the diamonds.

You are given 1 per defeated guardian and a total of 3 if you defeat the castle.

You can only get 3 crystals per battle.

When you win without defeating the guardians or castles you still get crystals.

Crystals need time once you've earned them to earn again (usually an hour or so)

Crystals and the castle look similar.