Hey, folks, do me a favor, wouldja?
Turn in your Monster Manual III to the Bonedrinker entry. 11-die undead, with unholy vigor, so these guys have 11d12 + 22 hit points. They have Damage Reduction, Energy Resistances (including sonic), and move pretty fast for the walking dead.
They have four attacks. They start a grapple automatically when they hit with tentacles, have a terrific chance to grapple and pin people, and then start doing 1d6 Con damage a round. They make spawn.
I'm trying to figure out how these critters are considered CR 6.
Going by that CR, I threw five of them against my 8th-9th level party this weekend. It was very close to a TPK.