Archvile

Run! Any character surprised by Archvile, needs to pass a DC 15 Constitution saving throw. If they fail, they are panicking for their next turn and can only do rolls at a disadvantage.

Multiattack. The archvile makes four attacks: one with his flame lake and the other three with his fire wave.

Flame lake. Archvile summons a 2 feet (3 meters) wide flame lake anywhere he can see. If it behinds beneath a character, they can make a DC 15 Dexterity saving throw to dodge it. The flame lake deals 3d6+8 fire damage, and disappears at the start of archvile's next turn.

Fire wave. Ranged Magic Attack: +10 to hit, reach 30 ft., one target (unless they're behind each other). Hit:  14 (2d6 + 6) fire damage, and the target must succeed on a DC 20 Constitution saving throw or be pushed 4 ft (6 meters) back.

Teleport. The archvile can use a bonus action to magically teleport, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space (it can be behind a wall, but not behind two of them). When he does that, he leaves a red trail behind him (for k2 turns), so anyone can see where he went.

Summon WARNING: Use only if you wish to give your players a really, really bad time.
Upon creating a Fire shield, Archvile can use his bonus action to start summoning 2 (d4+1) random creatures (roll d10):
1 - 4: Imp
5: Bearded Devil
6: Barlgura
7: Vrock
8: Gargoyle
9: Cacodemon (or a Spectator)
10: Dretch

The creatures start to take a fiery form in a place Archvile wants to summon them, and cannot be killed or even hurt before they spawn.
To summon them, Archvile has to stand still for three turns. If he is disturbed in any way (by taking damage, freezing, stunning etc.) the summoning action is cancelled and none of the creatures spawn. The summoned enemies have a minimal amount of HP.

Fire shield Archvile can summon a fire shield to defend himself against incoming attacks. He uses it as his regular action and cannot do anything else (except for resurrecting and/or summoning). The shield has 36 temporary HP and defends archvile from attacks coming only from one side he picks.

Resurrection Archvile can use a bonus action to resurrect up to 3 of any dead EVIL creatures within 2 feet (3 meters) to fight on his side. Such creatures however have their minimal amount of HP.