Nodes

[Endoperez]

Chaos Node:
A mix of Foul Spawn would fit well. You can use RanDom to add in random creatures of the Crossbreeding spell by creating a list of all the creatures it can summon and then adding in units from that list. Manticore, demon knights, and abysian Demonbred would all fit well. Summer Lions and Fire Snakes would also work.

Nature node:
Basilisks, cockatrices, elementals a Wyrm commander and Fall Bears are easy. One or more of: Crusher, Golem, Granite Guardian/Marble Oracle could replace Colossus. There are size 4 Giant Spiders and size 6 Hunter Spiders. You've already listed Catoblepas and Tarrasque. Perhaps Apmiphteres, Monster Toads, Couatl or two...

Sorcery node:
You can make Water Dragon have Air magic instead of Water, and equip it with Spirit Helmet. Replace Phantom Beasts with Grey Knights and/or Nether Warriors. Winter Wolves and Spring Hawks both fit.

Draconians could go into either Nature or Sorcery.