What exactly did Eirin mean with 'captured'? Would Mokou be teleported to another dimension or get mummified by countless talismans? And what does Eirin mean with 'run around working up a sweat'?
Beating/Surviving a boss's spellcard/nonspell without bombing or dying, so that you'll get the spell bonus, is what players call "capturing a spell". You can also capture a spell simply by surviving until the timer hits zero, after which the current healthbar is automatically depleted.
Ah...The letters of the charm...Oh, come to think of it, Eirin said,Just so you know, this is a survival spell.※A fixed time spell that has you run around working up a sweat, but as long as you survive until the time runs out, you're good.What a relief!Huh...?Yes, yes! We were so confused we misunderstood her...Damn it! I'm sure she knew that and was enjoying every second of it!!Phewwwww!