I’ve heard if the Mob casts it more than once, it makes it harder to drop. I don’t know if that’s bull crap or not.

It’s really all about RNG. Some I get in 1 run, others multiple runs. I’ve run Titan a ton of times and nothing yet. I just did Ramuh and got it in about 3 tries. RNG is RNG. Most of the open world spells I got in 1 try accept Acorn which took an eternity.