Master Thief Cat

Master Thief Cat is a demon found in Iris and the Giant.

"As long as this feline is here, each enemy attack will make me lose a card."

Location
In Path of the Giant, the Master Thief Cat appears on Floors 7B & 7W on all difficulties, and also Floors 3B, 5 & 14 on Nightmare difficulty.

In Path of the Ferryman, it appears on Floors 3 & 14B on all difficulties, and also on Floor 23 on Nightmare difficulty.

Strategy
While the Master Thief Cat is in battle, all enemy attacks will remove a card from your deck. The Master Thief Cat itself will start with 2 Armor and deal 2 damage to you.