It might not be necessary, but it might be useful to add a line of information to the lexicon index that the g.s. also requires mana like its lesser version.
Im not sure how mana costs are calculated; be it mana/second or mana/movement.
In the latter case, this might lead to higher costs (Overall feeling), or in the first case drain mana even when not using it. Those are the kind of details that might be worth mentioning.