Feats

Cold Caster

Prerequisite
Level 4+
Ability Score Increase
+1 Intelligence or Wisdom or Charisma
Source
FRHoF

You gain the following benefits.

Cantrip

You learn the Ray of Frost cantrip. If you already know it, you learn a different Wizard cantrip of your choice. The spell's spellcasting ability is the ability increased by this feat.

Frostbite

Once per turn when you hit a creature with an attack roll and deal Cold damage, you can temporarily negate the creature's defenses. The creature subtracts 1d4 from the next saving throw it makes before the end of your next turn.