Body and Soul

Body and Soul is a shield rune, so it aids the player on the more defensive side of things. Its rank is 15+ and costs 12800.
==Effect==
Every 300 seconds, gain a Soul Heart. Max 3. Increase max limit of Soul Hearts by 1+ per rank (max +5 ).
Edit; did try this rune, and even though I have it, I gained no Soul Hearts. And even if it worked, as there are only 1200 seconds in a game, upgrading it past level 1 would be a waste, as heart number 4 would spawn it at the end of the game.