You simply interact with the environment via your troops or minions. Sacrifice takes a much more personal twist on combat. The character you play is a wizard, a familiar of the gods if you will. He is charged by the gods with a task to fulfill in order to right some wrong that has been committed in their lands, or to somehow further their frequently nefarious plans. As a wizard, you are quite weak physically speaking, however you have a vast repertoire of magical spells at your disposal that can be employed to gain the upper hand on your opponents.
Spells use the standard magical fuel known as mana.
Every time you cast a spell, you loose some of your mana. In order to regain mana, you must travel back to your altar, you link to your god, and there your mana will slowly recharge. By creating a structure known as a manalith, you can prevent your enemies from using that particular mana rift. By creating creatures known as manahoars, you can be remotely attached to your manaliths, and even when you are away from your manaliths, your mana can be recharged by these creatures. Movement is generally like a standard 3rd person RPG or action game.