Codex of the Black Sun includes a focus called Savage Sorcery (p. 91), along with rules for spellcasting.
Savage Sorcery's level 1 use is described as a "Main Action invocation". While "Invocation" is occasionally used throughout the Codex of Dark Sun as a synonym for "Spell", it's equally used to refer specifically to the vocal part of spellcasting.
So the question is: What parts, if any, of the "Casting Spells" rules on page 21 apply to Savage Sorcery? Specifically:
Does it have to be declared at the beginning of the turn (and presumably would then be subject to failure on injury)?
Can it be used in armor?