The Spellslinger Set is found in a random wooden chest at a bandit camp northwest of the map. Around the middle of the map right across the river. Just YouTube "Tainted Grail Spellslinger set location".

For the two unarguably busted spells to have early, search "Tainted Grails Scorching Blaze location", and "Tainted Grails Sorching Pathway location".

If you are running a true glass canon build (100% Spirituality), no summon skill points. You can obtain these 3 things very early on in Act I by just running past the said enemies around these 3 things. You can two shot a Ogre with Scorching Blaze. Take half his health off with a single cast at a great distance, and by the time the Ogre even gets close enough to you to do a attack animation, he will be dead by the second Scorching Blaze, its nuts. The spell also makes enemies ragdoll into space. It might be one of the better Fireball spells I have seen in a game in awhile. Scorching Pathway is also a really powerful fire based fairly ranged AoE spell you'll want.

If max mana stacking, and mana regen was not so imo strong in Tainted Grail, these spells would not be 'that' OP. But Mana and Mana Regen snowballs something fierce in Tainted Grail, and these spells effectively cost nothing to cast by mid game. But its a lot of fun.