A few of my favorite spell card effects in FMW

Chapter 20, Nitori, Water Sign "Kappa's Pororoca": All units inside the spell area are treated as being underwater

Chapter 24, Suika, Oni Sign "Missing Power": Suika's size stat changes from S to LL

Chapter 34, Yukari, Barrier "Curse of Dreams and Reality": Yukari gains access to all spirit commands that the party can use

Chapter 38, Tewi, "Ancient Duper": Splits battlefield into two zones, one of which raises power by 50 and one of which lowers power by 50 at the end of the turn. The descriptions just say "Lowers power?" and "Lowers power?!" so you have to guess

Chapter 41, Keine, Future "New History Of Phantasm -Next History-": All units in the field have their level reduced by 25

Intermission 2, Reimu, "Fantasy Nature": Reimu's evasion rate +200%

Chapter 52, Parsee, Jealousy Sign "Green-Eyed Monster": The more points and WP you've invested into upgrading a unit, the more powerful Parsee is when fighting them

All of them are great, but that last one, damn

YEAH that's such a sick idea for a jealousy youkai