V Domain

 I fully admit to not really having any idea how balanced it is

>Domain power: You gain the swallow whole ability, and the ability to open your mouth wider than it should. You can devour a creature up to one size smaller than you at the time you used this ability, and hold in your extradimensional stomach one creature 1 creature a size smaller, 2 creatures two sizes smaller, four creatures three sizes smaller, 8 creatures four sizes smaller, and so forth. Inside your stomach creatures take 2 points of bludgeoning and 2 points of acid damage a round per cleric level. They can cut their way out by hitting AC 10 + 1/2 your normal AC bonuses (armor, deflection, natural, etc), and dealing twice your HD in damage in one round. Muscular action closes the hole afterwards.

>To swallow a creature you must be grappling them, and succeed on a pin attempt. Instead of pinning them, you swallow them. If you have a bite attack, you gain improved grab for your bite attacks and may subsequently swallow them.

>1: Swallow deals (HD/2)d4+str/2 bludgeoning and acid mixed damage/round
>2: Can cast enlarge person/monster on self, stomach acts as one size larger than your normal one
>3:Gain fast heal = half damage done to those in stomach
>4:Swallow deals  (HD/2)d6+str bludgeoning and acid mixed damage/round
>5:Can grown up to 3 size categories when using enlarge on self, stomach acts as 3 sizes larger
>6:Gain regen/- =half damage done to those in stomach
>7:Swallow deals  (HD/2)d8+1.5*str bludgeoning and acid mixed damage/round
>8:Can grow to colossal size, stomach can store up to colossal sized prey
>9th: Devour Soul (D&D wiki spell, as trap the soul but traps target's soul in caster, heals caster for 10 points of damage per CR of the target creature, and caster's body can hold an unlimited amount of souls) (maybe a modification/feat where they have the option to cast this immediately if someone dies due to their swallow whole attack if they can cast it?)