Heroes 5.5 WarGame Edition - Tactical Edition.

Read about it in the perk description on page 1. Yes, once and weekly, manticores join the hero's army. The same goes for wolves (but daily).

It's hard to find there anyway.

In general, I think having spells in the spell wheel, as well as army growth, is a detrimental thing.
Army growth is the job of castles and dwellings. Spells are the job of cities (not even treasure rooms), but there might be an exception here.
I see the game on the map more as a strategy game than an RPG.