Phase 1: Eldritch Power

Multiattack. Abdul sends out a shadow bolt and tentacles at the players.

Shadow Bolt. Ranged Weapon Attack: +4 to hit, range 5/30 ft., one target. Hit: 18 (1d12 + 6) necrotic damage.

Tentacles. Ranged Weapon Attack: +2 to hit, range 5/30 ft., one target. Hit: 17 (1d12 + 6) bludgeoning damage. Target is grappled, DC 15 to escape.

Impale. Abdul impales a player in melee range with his staff.

Impale. Melee Weapon Attack: +4 to hit, reach 5ft., one target. Hit: 33 (1d20 + 15) piercing damage. 

Phase 2: The Necronomicon (begins at 50% HP)

Multiattack. Abdul attacks the minds of his enemies with the Necronomicon.

Mind Destroy. Ranged Weapon Attack. range 5/30ft., one target. Hit: 23 (1d20 + 5) psychic damage. Can become immune to this attack with a DC 15 sanity saving throw. 

Invade Mind. Ranged Weapon Attack. range 5/30ft., one target. Hit: 10 (1d8 + 2) psychic damage. Target is afflicted with a short term madness effect. Can become immune to this attack with a DC 15 sanity saving throw.

Multiattack. Abdul calls upon the gods with the Necronomicon.

Giant Tentacle of Cthulhu. Summoned attack. +2 to hit, 15 ft. line that is 12ft. wide. Hit: 18 (1d20 + 0) bludgeoning damage. 

Laser Eye of Yog-Sothoth. Summoned attack. +3 to hit 25 ft. line that is 9ft. wide. Hit: 18 (1d20 + 0) necrotic damage. 

Abdul sends his staff into the ground and channels eldritch power through the walls of the tomb, causing the tomb to start collapsing.

Collapse (Costs 3 Actions). Abdul causes the tomb to collapse, dropping rubble on the players. DC12 to determine whether or not rubble falls on the player, does 20 (1d20 + 1) bludgeoning damage if rubble falls on a player, player is stunned, DC 15 strength saving throw to escape, other players may help the player escape.