The 4d6 came from post 586. I'd be happy with 2d12, though; the average is slightly lower, but higher values are more likely. Sure, let's do 2d12+13 or 2d12+26:
Reflexive Thrashing (Ex): Whenever a nay-churr takes at least 1 point of damage to its gizzard, the creature immediately flies into a state of panic and convulsion. This reflexive thrashing lasts for 1 full round. During this time, the nay-churr moves at quadruple speed (normally 40 ft.) and any creature within its reach must succeed on a DC 38 Reflex save or take 2d12+13 points of bludgeoning damage. Creatures inside the nay-churr's gizzard suffer 2d12+26 points of bludgeoning damage, and must succeed on a DC 38 Reflex save to take any action (such as attacking the nay-churr's gizzard or making a grapple check to escape). The save DC is Strength-based.
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