Upon activation, one of Isaac's heart containers (if any) will be replaced by 3 Soul Hearts.
Consuming your final Heart Container will not kill Isaac.
The paw removes full hearts first, leaving you with at least a half normal heart before the rest of your heart containers are used up.
If used with a half normal heart remaining, the player can convert their hearts quickly, effectively quadrupling their health. This is especially useful against the final bosses. (Mom, Mom's Heart/It Lives!, Satan, Isaac, and ???.)
- Can be instantly reused with a very brief (less than 1 second) cooldown.
- Does nothing for ???.
- Using this item with the extra heart container from the Strength Tarot Card will provide 3 Soul Hearts, but another heart container will be removed upon exiting the room. If this is done while using only spirit hearts (besides the one heart container from Strength), the next heart container item will do nothing.
- This also applies for the Liberty Cap trinket.
- This is one of the items required to transform Isaac into Guppy. Picking it up and leaving it will still allow Isaac to transform into Guppy after collecting 2 other Guppy-related items.
- The Polaroid - Since the paw can turn your current character into a pseudo ???, it works well with The Polaroid once you use up all of your Heart Containers/get down to a half-heart, as the shield will always activate upon being hit.
- Whore Of Babylon - Allows Isaac to permanently stay in a cursed state for only having Soul Hearts.
- Dead Cat - Dead Cat synergises well, as the player can effectively begin each new life as a pseudo ??? by using Guppy's Paw on their single heart container.
- The item seems to be based on the Monkey's Paw. This comes from the fact that the Monkey's Paw grants three wishes and a disaster happens to you, while Guppy's Paw grants three spirit hearts and you lose a container heart. Their names are also similar and both are the paw of an animal.