Board Thread:Questions and Answers/@comment-26581304-20151215232602/@comment-24577221-20151216003516

Low-level monsters are easier to feed than high-level monsters; their demands are simpler. Teleporting monsters once they've leveled up sufficiently makes room for new lower-monsters. And of course you need to keep feeding monsters, so you can accrue XP, so you can advance in the game and unlock more features.