The guide of which species are related, and can therefore be crossbred without the use of Crossbreed Potions.
Species Complexes List
I’ve been experimenting with the breeding system, and found that some species/breeds can be readily interbred, which you may not initially be aware of without attempting it yourself.
For context, the various “complexes” described in this guide will all be able to interbreed with one another without the use of Crossbreed Potions.
The Wolfhound Complex
- Hell Hound
- Wolf
- Dread Wolf
The Rat Complex
- Water Rat
- Spiny Rat
- Battle Rat
The Bear Complex
- Snow Bear
- Black Bear
The Panther Complex
- Panther
- Swamp Panther
The Varanus Complex
- Varanus
- Dire Varanus
- Black Varanus
- Sea Varanus
The Ghyllow Complex
- Ghyllow
- Ghyllow Beast
- Ryorodon
The Dragon Complex
- Reaper Dragon
- Swamp Dragon
The Hunterbug Complex
- Hunterbug
- Northern Hunterbug
The Red Velvet Spider Complex
- Redleg Spider
- Velvet Spider
The Worm Complex
- Harvest Worm
- Vampire Worm
- Horid Worm
I believe that there is only one final complex I need to add, and that is the surprising “Arachnid Crab Complex” which supposedly contains the Cave Arachnid and the Scavenger Crab, but I need to test it out myself because those Insectoids don’t really look anything alike and AFAIK they are never stated to be related in-game.