At 18th level, a Wizard gains the feature Spell Mastery. It reads:
At 18th level, you have achieved such mastery over certain spells that you can cast them at will. Choose a 1st-level wizard spell and a 2nd-level wizard spell that are in your spellbook. You can cast those spells at their lowest level without expending a spell slot when you have them prepared. If you want to cast either spell at a higher level, you must expend a spell slot as normal.
Early in Merlin's career, they learned the shield spell. It's in their spellbook and they have it prepared almost every day. At some point in their life, they realized that the magic was in them all along and gained a level of Sorcerer. As such, they learned shield as a Sorcerer to free up a Wizard Prepared Spell slot for something else.
When Merlin reaches level 19 (18 Wizard/1. Sorcerer) they get Spell Mastery.
Can they still use the spell prepared as a Sorcerer for the Wizard feature?
The checkboxes I see are:
- [X] A 1st-level Wizard spell
- [X] A spell that is in your spellbook
- [?] You have [it] prepared
To my reading, it doesn't need to be prepared AS A WIZARD, just prepared. The question is, Sorcerers don't "prepare" spells, they "know" spells. But the PHB lumps those terms together. Is there a mechanical/rules difference and can Merlin keep the spell as a Sorcerer and use it with the Spell Mastery feature?