Abyss Maw (3.5e Feat)
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Abyss Maw [General (evil)]
The second stage of Flesh Eater allowing for the instant consumption of smaller creatures
Prerequisite: level 5, must be able to eat food normally, Evil Alignment, Flesh Eater 
Benefit: Your head can split open to reveal a whirling mass of tentacles, teeth, and eyes allowing the character to attempt to swallow any creature one size category or smaller than them that they have currently grappled (this follows the same rules as being swallowed) if they successfully swallow the creature they take the normal bite damage of the character and the same damage as acid each following round (this acid damages objects and equipment as well) as well as 2d3 crushing damage until either death or regurgitation (when a creature is swallowed they can deal damage to force regurgitation however any creature with this feat has a bonus dr10 to internal damage and gets to make a concentration check of dc5 +total damage dealt by that creature each time it takes internal damage this DC increases by 5 each round until the creature is either regurgitated or dies). this causes anyone not savage or evil aligned to make a dc15 + character's level will save or be terrified for 1d6 rounds at the sight of the whirling abomination that was once a head (if this has been seen multiple times the DC goes down unless the target is good aligned or squeamish) this also allows for the character to gain an acid globule breath weapon (fires a ball of acid in a 5ft aoe range is a base of 20ft) on a 1d6 rounds cooldown this acid does the same damage as the character in questions bite attack and does damage objects and equipment.
Normal: you have none of this
Special: also when eating a fallen creature you gain 1/2 your class level of hp (treated as magical healing) provided they were either swallowed whole or you dedicate an entire round to eating them