Heart of Gold

Strategy and Synergy
This artifact can be a life-saver later in the game, specially if you're aiming for a Genocide run. The Defense penalty is a little harsh, but by the time you're nearing the Eden's gate you probably got some or perhaps, a.

Acquiring this artifact early in the game is not recommended. Not only it is pretty rare, but also the health gain can be achieved through other methods. If aiming for a Pacifist run, you'll seldom use it due to the end-of-level heal granted by spared bosses. The +1 to Attack & Spell damage doesn't worth as much as the full heal this artifact provides, so if aiming for an increase in either stats, and  are much more viable options.