Navery:
Likewise on my mage/tamer (magery/EI/med/taming skills).
Just stand close to a dragon (no other pet really works for me here), heal with bandages, and cast fireballs with a spider slayer spellbook.
Reknowned: A combination of beetle/bake kitsune works best for the spawns with fire ants/fire demons (make sure the bake is out of the stables first!). Only spells I use is greater heal. For the rest, either a beetle/nightmare, cu sidhe or greater dragon are fine (but the dragon is slow!). Against the pixie, using a dragon is far-and-away easiest.
Medusa: Stay invised, kill the statues before they become evil pets and you're fine. If you show yourself, then you spend a lot of time running away... so a cu sidhe works best for me here. Just cast heal as-needed.
Stygian Dragon and Slasher of Veils: Forget it, your pet doesn't stand a chance (I've tried all of my pet combos against the slasher, the closest was a single bake kitsune and I still didn't get far).
