RTF is a global modification that replaces all towns in the game.

We didn't want to make a thunderbird because of the presence of simurghs and coatls on the phoenix model; I want to make Rukh birds neutral. By the way, there's a Rukh head model from the sixth game in one Polish mod.

There are many model parts from the sixth game in Polish mods: a Necromancer's helmet, spider legs, a High Rogue head, and, if I remember correctly, claws from Mother Namtaru (those claw-like hands, or something like that). And that's not all; I even saw a model of Kirill.
I just remembered that in the game "Eador: Masters of the Broken World," there's a storm dragon (in version 1.4 and higher). It has a rather interesting color, and you could take some textures from it.