Probably vs spellbook are good for the swarm, and spellbook is pretty weak vs swarm, but vs amazoness nah, amazoness 🔥 them easily (except if fur hire manage to destroy onslaught before)
Isn't ignition is a legacy rule now? Which means you can't activate your non-quick monster effect right after summoning them anymore. But even if you can use ignition, they can still chain fate to your effect, banishing your monster first anyway. Unlike spell/traps, many monster effect stop working as soon as the monster is gone.