Chromatic Catalyst (Green)

Agitating Presence. Creatures within 15 feet of the Catalyst have disadvantage on saving throws against a dragons breath attack.

Adapted Anatomy. The Catalyst is immune to the effects of a dragons breath attack. 

Flyby. The Catalyst doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Multiattack. The Catalyst makes three claw attacks.

Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d4 + 5) slashing damage plus 3 (1d4) poison damage.

Virulent Claw (3/day). The Catalyst coats its claws with a potent venom. Once coated the venom retains its potency for one minute, or until the Catalyst hits a creature with its Claw. When a creature takes damage from the coated claw it must succeed on a DC 16 Constitution saving throw or become vulnerable to Poison damage until the end of the Catalysts next turn. If the creature has a resistance to Poison damage, the resistance becomes nullified instead for the duration.

Primed Malice (2/day). The Catalyst reacts when a dragon it can see within 60 feet is about to use a breath attack and uses Virulent Claw if available. Before the breath attack is made, the Chromatic Catalyst can move up to its speed, and make a Claw attack.

The Catalyst must end its movement closer to the dragon than where it started.