1up!

1up! is a passive item.

Effects

 * Isaac gains an extra life.
 * On resurrection, the mushroom that follows Isaac will disappear and Isaac will respawn with all his previous Red Heart Containers at full health.
 * If Isaac has no red heart containers, he'll respawn with 1/2 Soul Heart instead.

Seeds
LDPB D0QG (X-Ray Vision adjacent to spawn, first secret room to left from spawn, unless you have Forget Me Now unlocked) CWSQ TNM8 (first secret room right from spawn)

Trivia

 * This is a reference to the Mario franchise, where collecting a green mushroom would give you an extra life.

1up!