Codex of the Black Sun includes an approach called Savage Sorcery (p. 91), along with rules for spell casting.
The use of level 1 Savage Sorcery is described as a "main action invocation." While "Invocation" is occasionally used throughout the Dark Sun Codex as a synonym for "Spell," it is also used to refer specifically to the vocal part of the spell casting.
So, the question is: What parts, if any, of the "Casting Spells" rules on page 21 apply to Savage Sorcery? Specifically:
Should it be declared at the beginning of the shift (and presumably it would be subject to failure due to injury)?
Can it be used in armor?