Fire Aura. At the start of the Hellrider's turn, each creature within 5 ft takes 4 (2d4) fire damage, and any flammable objects in the aura that aren't being carried or worn ignite. A creature that touches the Hellrider or hits it with a melee attack while within 5 ft of it takes 4 (2d4) fire damage.

Spellcasting. The Hellrider is a 6th-level spellcaster. Its spellcasting ability is [ability score] (spell save DC #, +# to hit with spell attacks). The Hellrider has the following Sorcerer spells prepared:
Cantrips (at will): Fire Bolt, Dancing Lights, Chill Touch, Minor Illusion

1st level (4 slots): Charm Person, Burning Hands, Magic Missile

2nd Level (3 slots): Shatter, Scorching Ray, Darkness

3rd Level (3 slots): Fireball, Fear, Lightning Bolt

Devil's Sight. Magical Darkness does not impede the Hellrider's Darkvision.

Magic Resistance. The Hellrider has advantage on saving throws against spells and other magical effects.

Charge. If the Hellrider is mounted and moves at least 10 feet straight toward a target and then hits it with a Lance attack on the same turn, the target takes an extra 8 (2d8) piercing damage. If the target is a creature, it must succeed on a DC 16 Strength saving throw be knocked prone.

Multiattack. The Hellrider makes two attacks with its Nine Lives Stealer

Nine Lives Stealer. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 7) Slashing damage plus 4 (1d8) fire damage.

Lance. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 11 (1d12 + 5) piercing damage plus 4 (1d8) fire damage.

Crossbow, Heavy. Ranged Weapon Attack: +7 to hit, range 100/400 ft., one target. Hit: 9 (1d10 + 4) piercing damage.