Reduce Size. As an action once per day, the efreeti can reduce its size to Medium for 1 hour. It's clothing and possessions also reduce in size as long as they are in his possession. This size reduction has no further effect on his abilities.

Cunning Action. On each of its turns, the efreeti can use a bonus action to take the Dash, Disengage, or Hide action.

Elemental Demise. If the efreeti dies, its body disintegrates in a flash of fire and puff of smoke, leaving behind only equipment the efreeti was wearing or carrying.

Feint. On each of its turns, the efreeti can use a bonus action to make a deception Charisma check against a target within 5 feet. That target makes an Insight Wisdom check to see through the feint. If the target fails this check, the next attack roll against the target by the efreeti has advantage if the attack is made before the start of its next turn. 

Grant Wishes. As described in the MM p 144, the efreeti is capable of granting the spell Wish three times to a non-genie.

Innate Spellcasting. The efreeti's innate spellcasting ability is Charisma (spell save DC 17, +9 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

At will: detect magic

3/day each: enlarge/reduce, tongues, invisibility,

1/day each: conjure elemental (fire elemental only), gaseous form, greater invisibility, major image, plane shift, wall of fire

Sneak Attack (1/turn). The efreeti deals an extra 14 (4d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the efreeti that isn't incapacitated and the efreeti doesn't have disadvantage on the attack roll.

Suave Defense. While the efreeti is wearing light, natural or no armor and wielding no shield, its AC includes its Charisma modifier.

Multiattack. The efreeti makes three scimitar attacks or uses its Hurl Flame twice.

Scimitar. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage plus 7 (2d6) fire damage.

Hurl Flame. Ranged Spell Attack: +9 to hit, range 120 ft., one target. Hit: 17 (5d6) fire damage.

Riposte. When a creature misses the efreeti with a melee attack, he can use his reaction to use his feint ability and make a melee attack against the creature.