Heart

An uncommon Guts set neck armor with multiple acquisition routes: found in The Core chapter, from the Dying Fetus event (choose to kill the fetus), or from The Throbbing Domain's Meat Altar by sacrificing a cat (requires a Luck check). Grants +2 Constitution and +1 Health Regen. The Guts set organ pair with Liver, providing a solid passive sustain foundation. The Meat Altar route adds stakes — you're gambling a cat for the drop.

The Heart's stats mirror the Liver exactly: +2 CON and +1 Health Regen. Together the pair provides +4 CON and +2 Health Regen passively, with no Shield or negative tags. The neck slot on a Guts set build is cleanly occupied by the Heart, making it a no-downside upgrade over empty slots or weaker early neck armor. The Meat Altar acquisition adds a run-specific risk: you lose a cat companion to potentially get this uncommon item.

Equip with Liver for the full Guts set and maximum CON/Regen payoff. The multiple acquisition routes make it one of the more accessible uncommon neck armors in the game. The Meat Altar route is only worth attempting if your cat companion isn't critical to your build and you have good Luck — losing a companion for a failed Luck check is a steep price.