This is a very evil and very hungry tree. It has a hydra like concept, where the more you damage it, the more dangerous it becomes, but with a twist, since there is no real way to prevent more mouths from growing, but in exchange it doesn't regain HP upon regrowing a head.
This monster is meant to be at the opposite end of a treant. Where a treant bestows life to trees, this summons undeath. In addition it has a cheeky resistance to fire damage which could take players by surprise.
For Never-ending Hunger, I should probably add somewhere that the maws vanish after 24 hours, although it could make for a fun repeat encounter if the party bumps into one they failed to defeat previously.
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Take Care!