I love these little monstrosities from Planar Adventures, and would love to include them in a campaign in the future. My first question, though, is how the heck do I pronounce Wisagatcak?
Beyond that, these little buggars are nasty! They’re really good trippers, and with Greater Trip, having multiples of them swarming the group can rack up a lot of Attacks of Opportunity. Plus, they’re dealing 1 Wis damage per round with their 60’ Aura, and their Bites inflict 1 Str Drain. And, their 1/day Polar Ray deals 1d4 Dex Drain. They can go into Berserker Mode by just full-attacking on a single creature (Bite, Gore, 4 Talons, and Rake), for a couple rounds, and gaining Haste.
With Nimble Moves, Acrobatic Steps, See in Darkness, Tremorsense, 3/day Air Walk, and At Will Dimension Door, you can put these guys in the darkest, foggiest, craggiest, most unnavigatable environment, and they’ll run circles around the group.
How would you run these creatures? As a solo monster? As a group?
CR 14; +22 attack/+24 CMB actually isn't great against 14th level PCs. In the right environment one would make a decent enemy for a group of 10th level PCs to hunt down (with the environment being another enemy), but the waves of these creatures suggested in the description against higher level PCs would be relying heavily on their polar rays, which is the sort of gamble which could be a waste or a TPK.
Its worth noting that they are able to Lunge from underneath the ground with Burrow Speed and Tremorsense. This means the PCs need to get away from the ground ASAP or they are just going to be attacked relentlessly from below without being able to respond. Once the party has taken to the air, the Wisa can pelt them with Freezing Spheres or trap them in 15ft Domes of Wall of Ice in order to prevent them from flying beyond their reach.
I doubt tripping is their best tool between these tactics.
My first question, though, is how the heck do I pronounce Wisagatcak?
The name comes from a Native American trickster spirit that is variously called Wisekedjak, Weesack-kachack, Wis-kay-tchach, etc. It's sometimes corrupted to "Whiskeyjack." (Neil Gaiman's American Gods used both that and Wisakedjak.)