Entity: Spell Blending

Source Core Rulebook pg. 206 ^4.0

You theorize that spell slots are a shorthand for an underlying energy that powers all spellcasting, and you've found a way to tinker with the hierarchy of spell slots, combining them to fuel more powerful spells.

When you make your daily preparations, you can trade two spell slots of the same level for a bonus spell slot of up to 2 levels higher than the traded spell slots. You can exchange as many spell slots as you have available. Bonus spell slots must be of a level you can normally cast, and each bonus spell slot must be of a different spell level. You can also trade any spell slot for two additional cantrips, though you cannot trade more than one spell slot at a time for additional cantrips in this way.