In Digimon Frontier, chosen children like Koichi Kimura can use the itemised spirits of ancient Digimon to Spirit Evolve into Digimon themselves.
Koichi uses the Human Spirit of Darkness to become Loweemon, and the Beast Spirit of Darkness to become KaiserLeomon. Though we never see it on-screen, by combining the spirits, he can become Rhihimon.
While we never see it happen in the anime, certain sources suggest that Tommy could have become Liollmon under certain circumstances.
These powers come from the spirit of the ancient legendary warrior, AncientSphinxmon of the Ten Legendary Warriors.
Note: That is the worst, goofiest fucking Liollmon illustration in the entire card game. Sorry, illustrator, but it just is.