School: Chronomancy (Transmutation)
(Intended for use with the Chronomancer subclass)

By use of an Extension spell, the caster prolongs the duration of a single previously cast 1st-, 2nd-, or 3rd-level spell by 50%. Thus, a Levitation spell can be made to function up to 15 minutes (rather than 10), a Hold Person spell made to work for up to 90 seconds (rather than 60), etc. Naturally, the spell affects only spells that have a duration. This spell must be cast immediately after the target spell which the caster wishes to extend, either by the original caster (extend one's own spells) or another spellcaster (extend someone else's spell). If one full round or more elapses between the target spell's casting and the casting of Extension, it cannot be extended, and this spell fails, and its slot wasted.

At Higher Levels:
4th level slot - This spell is the same as the 3rd-level slot Extension spell, except it extends the duration of 1st-through 4th-level spells by 50%.
5th level slot - This spell is the same as the 3rd-level slot Extension spell, except that it will extend the duration of 1st- through 3rd-level spells by 100%, and will extend the duration of 4th- and 5th-level spells by 50%.

Inspired by the 2e AD&D Wizard spells Extension I, Extension II, and Extension III.