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card
defect
skill
rare
Rainbow gives you an easy way to quickly fill up your orb slots. If you can make good use of the orbs, it can be a decent amount of DPS with enough focus. When your powers and exhaustible cards are gone, you can play it fairly frequently so long as it is upgraded. With little focus, I would not consider upgrading it.

Data Disk
common
Start each combat with 1 Focus.
B+

Inserter
boss
Every 2 turns, gain 1 Orb Slot.
A

Runic Capacitor
shop
Start each combat with 3 additional Orb slots.
B

Toxic Egg
uncommon
Whenever you add a Skill card to your deck, it is Upgraded.
A

Dead Branch
rare
Whenever you Exhaust a card, add a random card to your hand.
B-

Snecko Eye
boss
Draw 2 additional cards each turn. Start each combat Confused.
A-

Velvet Choker
boss
Gain 1 Energy at the start of each turn. You cannot play more than 6 cards per turn.
A

Pocketwatch
rare
Whenever you play 3 or less cards in a turn, draw 3 additional cards at the start of your next turn.
C-