Magic weapon for Unchained Rogue 5 / Magus 3

[TyroAmberhelm]

I've come up with a custom magic item in my game and am just looking for some feedback particularly if you guys think this is too OP for an unchained rogue 5 / magus 3

+1 Rapier

3 levels of spell storing (3-1st, 1-1st and 1-2nd, OR 1 3rd)
He can use these spells per the Magus spell strike ability

He can also throw the weapon and trigger the spells per the Magus spellstrike ability. The weapon boomerangs back to him.

He can also choose to trigger ALL of the spells at once. (1 or all)

The weapon has a bit of a backstory and he is a pretty unpredictable character so I was considering making the weapon "broken" somehow or adding some kind of Wild Magic feature to it. I was thinking this would offset the power of the weapon.

For flavor ideas, the weapon was created by a gnome earth wizard.

What do you think? Too OP? any other cool ideas?

[TyroAmberhelm]

Nobody?

[Cyrad]

Letting you spellstrike with it for free would make this really expensive to compensate. Letting you use it as a boomerang AND trigger the spellstrike spellstoring ability would jack up the price to ridiculous levels because that totally negates all of the drawbacks of the spell storing ability.

Triggering all of the spells at once, however, is totally broken. You can already do some pretty cheesy stuff with spell storing weapons. This ability cranks it up to 11 by breaking the rule that anything can only cast a spell once per round unless they have a swift action spell. It's also ridiculous in the hands of a magus, who can already nova spells.

[TyroAmberhelm]

Thanks for the feedback Cyrad.
What are the drawbacks of spellstoring?
What is Nova?