There are a total of 10 Ancient Digimon. Each one represents an "element": Fire, Light, Ice, Wind, Thunder, Darkness, Steel, Earth, Water, Wood. From there, are two Spirits for each element. One is the "Spirit H" (H stands for Human) and one "Spirit B" (B stands for Beast). Using a Spirit H results in a very humanoid Hybrid Digimon, while using a Spirit B results in a more beast-like Hybrid.
 

Spirit of Fire H (from AncientGreymon)	Spirit of Fire B (from AncientGreymon)
Spirit of Light H (from AncientGarurumon)	Spirit of Light B (from AncientGarurumon)
Spirit of Ice H (from AncientMegatheriumon)	Spirit of Ice B (from AncientMegatheriumon)
Spirit of Wind H  (from AncientIrismon)	Spirit of Wind B (from AncientIrismon)
Spirit of Thunder H (from AncientBeetmon)	Spirit of Thunder B (from AncientBeetmon)
Spirit of Darkness H (from AncientSphinxmon)	Spirit of Darkness B (from AncientSphinxmon)
Spirit of Wood H (from AncientTrojamon)	Spirit of Wood B (from AncientTrojamon)
Spirit of Earth H (from AncientVolcamon)	Spirit of Earth B (from AncientVolcamon)
Spirit of Steel H (from ?)	Spirit of Steel B (from ?)
Spirit of Water H (from AncientMermaimon)	Spirit of Water B (from AncientMermaimon)