Fiendwurm



That is in fact the correct spelling for this worm, do not ask why they spelled it like that, no one knows. So here we have a monster which is tied for the highest CR in the monster manual, and it is a big ass worm. Modified by some vague demonic powers it posses a portal to the abyss in its stomach and it is far from happy about it, so it takes out its anger on the nearest creature.

In terms of combat is has one attack, a decent bite though at the level it is supposed to be fought at, that is low epic, it is not very powerful at all, a freedom of movement will allow you to ignore the grapple which is good because being swallowed and portaled to the abyss is not a pleasant proposition when fighting something like this. One of the most dangerous things I see is the ability to summon 1d4 Jovacs, I don't know if you remember but they are the little buggers that reflect damage, and it can't be negated, meaning any unwary party member could easily put an end to a squishier member of the party.

Challenge Rating: This thing has a bases CR of 28, this is far beyond a level where a party could reasonably take it out, given its only really dangerous thing is sending people to the Abyss, which is just a quick plane shift to get back at high levels. With that load of HP it comes out to CR 23, but I think it's more reasonable at CR 20, facing maybe a level 15 or 16 party as a monster that has been rampaging through the country side.

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HP: 348/6 = 58 (24 HD)
AC: +3 (28)
Special Attacks: +4 (Improved Grab, Swallow Whole, Death Rift, Demonic Belch)
Special Qualities: +5.5 (Acidic Hide, Dr 15/-, Acid immunity, Senses)
CR: 70.5/3 = 23.5