Cards

Cards are an item dropped by Enemies with a 12.5% chance. Upon getting 5 of them, you can go in your backpack and upgrade them for an Elite variant and one of the enemy's skills.

You can also upgrade the Elite cards once you have 5, granting a Super card, and giving your skill +1 tier.

There is a 3% chance a card can become Corrupted [obtainable from only c1+.] You can upgrade them and get the same skill, but SLIGHTLY more powerful, and 1 less SP [if it already costs 1 SP then it does nothing] Once again, you can get an Elite version, giving your skill +2 tiers, but it won't subtract SP needed to use.