At 20th level, the arcanist learns how to convert her arcane reservoir into spells and back again. She can cast any spell she has prepared by expending a number of points from her arcane reservoir equal to 1 + the level of the spell to be cast instead of expending a spell slot. When she casts a spell in this fashion, she treats her caster level as 2 higher than normal, and the DCs of any saving throws associated with the spell increase by 2. She cannot further expend points from her arcane reservoir to enhance a spell cast in this way.