I think he´s talking about a spell that you can obtain hacking in shadowkeeper. I cant tell you its name exactly cause i have the spanish version, but its something like "Nahals reckless alchemy". Its a level 1 spell, that consists on the following:
the mage chooses a spell from any level (he has to know it, that is have it written in the spellbook, but no need to have it memorised). Then he summons a powerful bunch of energy and tries to shape it into the desired effect. Normally he wont be able to do it, and anything can occur, either good things or disasters (like having cast a fireball at himself).
More or less this is what its
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"Let my spells do the dirty work" Ertai, High Sorceror of the Holy Flame