Transformation of Kadon options

So i am wondering what is the best creature to transform your slaughtermaster into from the lore of beasts?

I do not call myself experienced in this lore so i thought i would put it out there

Does your creature depend on your opponent? Your army? what models you own?

Now i am fortunate to own the dragon but should i get the other options if they will never get used

Let me hear your thoughts

Mine varies depending on opponent and which version I'm going to be rocking, but the Mountain Chimaera is pretty wonderful.

As for the models, that entirely depends on where you play.  Some places require the exact models, others just one of the appropriate base size.

Mountain Chimera goes rawr!  He's all you need.  If there is enemy left after you have done that then something has gone wrong.

Mountain Chimaera for combat, Big Dragon for Breath Weapon. Depends entirely on your plan.