Nerf-in-progress

Up to Shadow Snake or so
Rough nerf complete

Mostly halved everyone.  0-2 stayed put, the Jabberwock, Thing, and
Tripod are 10 IIRC, and the rest mostly around 3-6.  Critters top out at
6, Nasty stuff 7-9.
Merge pull request #5697 from KA101/Critter-combat-nerf

Critter combat nerf