Source: Arcana Unleashed
General Feat (Prerequisite: Level 4+, Familiar Friend Feat)
You gain the following benefits.
Ability Score Increase. Increase one ability score of your choice by 1, to a maximum of 20.
Elemental Energy. You learn how to imbue your familiar with elemental power. When you cast the Find Familiar spell, choose Acid, Cold, Fire, Lightning, or Thunder damage. Your familiar is imbued with this energy until you cast Find Familiar again, granting it the following benefits:
Elemental Resistance. Your familiar has Resistance to the chosen damage type.
Energy Pulse. As a Bonus Action, you command your familiar to unleash a burst of elemental energy. Your familiar must be within 120 feet of you and take a Reaction to unleash this burst. Each creature in a 5-foot Emanation originating from your familiar makes a Dexterity saving throw (DC 8 plus your spellcasting ability modifier for the Find Familiar spell and your Proficiency Bonus). On a failed save, a creature takes 2d4 damage of the chosen type, and if the creature is Medium or smaller, it has the Prone condition.