What skills should Necromancers take when facing Orcs on a very large map?

Lol, mass spells only cost 50% of initiative, and with spell mastery, it's only 20%. You'll be able to cast other spells almost immediately.

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I'd just like to point out an obvious mistake - the effects of "Spell Mastery" and mass spells do not stack (i.e., the shift on the initiative bar will still be 50%). ;)