Orcs need Void Embrace to recover from Tax. You can have an Orc sorcerer without Void Embrace, but he won’t last very long. One or two rituals and he’ll tax himself into unconsciousness or death.
The primary difference between human sorcery and Orc sorcery is in the spell lists. Orc sorcery is not as expansive and flexible as human sorcery. It encompasses both Summoning (Rituals of Blood) and Sorcery (Rituals of Night). The other difference is that Orc magic is a gift of the God of Blood and Darkness. The magic is controlled by the Servants, the cult of that terrible god.
Ah, I got that wrong. It is exactly like Sorcery on those pages. However, because you can’t resist tax without Void Embrace, you lose your Spell Ob in Forte and test for the sickness as usual. However, as per the overtax rules, for each point you would be reduced below 0 you take a BX wound where X = the spell Ob, and it’s cumulative. So Let’s say you have Forte 4 and you cast Death’s Howl. You are automatically taxed three points. Then let’s say that you cast it again, you’re now at two points below 0. You fall unconscious and take a B6 Wound.