In the book Tome of Battle, initiator classes gain maneuvers which are in a sense, comparable to a spellcaster's spells. But while an initiator must qualify with many lesser examples of a certain discipline before obtaining a high level example of the school, a spellcaster has no such limitation. This variant represents a minor nerf to a spellcaster's power in the form of requiring certain chains of spells from the same school, in order to obtain the higher level versions. This is both thematic, showing that one must have a mastery over, say, lesser transmutation, before one may polymorph into dragons at a thought, and provides a coherent theme to the caster as a whole.