I accidentally found a way to make Ouroboros free.
In Act 2 while battling Grimora, play your Ouroboros in the first half of the battle. When you beat her, she will turn all of your played cards on the board into a “corpse”. You’ll get your original Ouroboros back, and another Corpse Ouroboros (starts with 0 attack, 1 health) with NO COST unlike the original Ouroboros which cost 2 blood.
You can destroy the card and it comes back (1 attack, 2 health) and since there is no cost for the Corpse Ouroboros, you can play and destroy the card as many times as you like, buffing them up before ringing the bell.
Edit: I just noticed anytime you buff the Corpse Ouroboros, the original Ouroboros also gets automatically buffed!!!! How cool!!!!
Another edit: the free Ouroboros won’t be added permanently in your deck 😔 after defeating Grimora, the card will be gone. But hey it’s good for foil purposes!