Matryoshkasting

Requirements - Level 3

When you use a level 2 or higher spell, the next spell of a lower level that you cast costs 1 less mana. This can chain together until you spend 0 mana on casting a spell.

If a spell you cast is of the same level or a higher level than the one you cast last, the effect ends.

For the purposes of this feat, a spell is considered of a higher level when you upcast it.