Blightstraw Chimera

Goat Spellcasting. The Goat is a 5th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 14, +6 to hit with spell attacks). The Goat has the following wizard spells prepared:
Cantrips (at will): fire bolt, ray of frost, Mage hand

1st level (4 slots): magic missile, shield, ice knife

2nd level (3 slots): misty step, suggestion

3rd level (2 slots): counterspell, fireball

Multiturn. The chimera has three turns in initiative. One for the lion, one for the goat and one for the Dragon. The lion controls the walking speed, the goat can cast spells, and the dragon controls the flight.
Lion 15 AC - 100 hp
Dragon 17 AC - 80 hp
Goat 13 AC - 65 hp
When one of the heads dies, it can no longer take actions and the chimera can no longer use the movement type associated with that head.

Dragon Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage.

Lion Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

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

[spell]misty step can only be used as long as the goat head is alive.

The reaction spell [spell]shield can be used as long as the goat head is alive. The plus 5 bonus to AC can be applied to any one of the heads, and lasts until the end of the goat's turn.