Rage

In battle, you fight with primal ferocity. When you reach half HP, you enter a rage.

While raging, you gain the following benefits:

• You have advantage on Strength checks and Strength saving throws.
• When you make a melee weapon attack using Strength, you gain a +2 bonus to the damage roll.
• You have resistance to bludgeoning, piercing, and slashing damage.

Storm Aura

You emanate a stormy, magical aura while you rage. The aura extends 10 feet from you in every direction, but not through total cover.

Your aura has an effect that activates when you enter your rage, and you can activate the effect again on each of your turns as a bonus action. 

When this effect is activated, you can choose one other creature you can see in your aura. The target must make a Constitution saving throw. The target takes 2d8 lightning damage on a failed save, or half as much damage on a successful one. The DC equals 16.

Multiattack. The chimera makes three attacks: one with its bite, one with its horns, and one with its claws. When its fire breath is available, it can use the breath in place of its bite or horns.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 5) piercing damage.

Horns. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 10 (1d12 + 4) bludgeoning damage.

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 5) slashing damage.

Lightning Breath (Recharge 5–6). The dragon head exhales lightning in a 15-foot cone. Each creature in that area must make a DC 16 Constitution saving throw, taking 31 (7d8) lightning damage on a failed save, or half as much damage on a successful one.