Time Traveling Theory for Idiots (La Teoria dei Mutamenti Temporali in the original Italian) is a treatise of which Magica De Spell owns a copy.
Description[]
A heavy purple gold-bound spellbook, Time-Traveling Theory for Idiots is a treatise on time travel, specifically dealing with temporal mutability — the circumstances and side-effects of altering the timeline. For example, it documents that when using the Time-Tuner Vortex Spell, one should avoid interacting with the visited period of the past at all costs, at the risk of causing unpredictable changes to the present.
Behind the scenes[]
Time-Traveling Theory for Idiots appears in the 2007 story The Time Vortex.