The Dark/White Knight Steed = 5 energy only, random drop (much like dragons)
Demetria = 5+ guaranteed
Fanning Dragon = 5+ guaranteed
Hiss in Boots = 2+ guaranteed
Lady Treeple = 2+ guaranteed
Myra = 2+ guaranteed
For future reference, I pulled this info from the forum's HUB's Inventory Guide. If you look under the entry for Energy, Mod SpiritWind has listed every item, their minimum energy drops, if energy is a guarantee and a list showing the the energy amounts each style can drop.