Black-Dice Knight

Cursed Power. The creature is imbued with cursed energies and has 3 actions and 2 bonus actions per turn. It does not require air, food, drink, or rest.

Dice of The Ghost. Each of the creatures faces, one for each side of a four sided dice, imbue the creatures Melee Weapon attacks with a different type of damage. At the start of the creatures turn, it may change its current face to a face of its choice, changing the magical damage it's attacks do: 

1. Psychic
2. Poison
3. Necrotic
4. Thunder 

Spellcasting. The Black-Dice Spectral Knight is a 5th-level spellcaster. Its spellcasting ability is CHA (spell save DC 15, + 6 to hit with spell attacks). The Black-Dice Spectral Knight has following Warlock spells prepared:

• 1st Level (6 slots): Cause Fear, Unseen Servant, Witchbolt.
• 2nd Level (5 slots): Darkness, Invisibility, Ray of Enfeeblment.
• 3rd Level (4 slots): Counterspell, Fear, Summon Undead.
• 4th Level (3 slots): Blight, Sickening Radiance.
• 5th Level (2 slots): Negative Energy Flood, Scrying.

Summon Steed (1/Combat). The creature summons a Black Spectral Steed, it's familiar and mount, which it may ride into battle. This costs 1 action and increases the creatures AC by 3 and movement speed by 60 ft. and can only be used once per combat.

Smash. Melee Weapon Attack: +3 to hit, reach 5 ft., 1 target. Hit: 28 (2d20 + 8) Bludgeoning damage. This attack costs 1 Action.

Rush. Melee Attack: +5 to hit, reach 15 ft., straight line attack. Hit: 32 (3d12 + 8) Bludgeoning damage. This attack costs 2 Actions, the creature moves 15 ft. in a chosen direction, hitting any creatures in its path.

Trample. Mounted Melee Attack: +4 to hit, reach 5 ft., 1 target. Hit: 44 (3d20 + 4) Bludgeoning damage. This attack costs 3 Actions.

Eminence of Pain. The creature resonates with powerful magic, and can send a blast of magical damage in a wave shape 15 ft. in any direction, dealing 1d10 Force damage and pushing any affected creatures 10 ft. in that direction.

Vorpal Slash. When the creature is targeted for a Melee Weapon Attack, it can roll a DC 18 CHA check to open a rift leading 60 ft. from the creature to a point of its choice. If successful the ability creates a blast of Force energy that damages any creature within 5 ft. of the creature that cast the ability. The reaction deals 1d20 + 6 Force damage, and can only be used once per round.