Black Ice

You create a visible blackish resin that sticks to your whole body.
This resin prevents other spell-casters from targeting you while casting first level spells.
This affects harmful and beneficial spells.
You can still be hit by an AOE spell not directly targeted on you.

At Higher Levels.
When you cast this spell using a spell slot of 2nd level or higher, the spell protects you from being targeted by spells of a level less than or equal to the level of the spell slot you used. When you cast this spell using a spell slot of 3rd level or higher, the duration increases by 1 minute per spell level.