Blue Slaad (fighter variant)

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

Regeneration. The slaad regains 10 hit points at the start of its turn if it has at least 1 hit point.

Surge of fury. Once per long rest, on its turn, the slaad can push itself beyond normal limits for a moment, allowing it to take an additional action on its turn.

Multiattack. The slaad makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) piercing damage.

Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage. If the target is a humanoid, it must succeed on a DC 15 Constitution saving throw or be infected with a disease called chaos phage. 

Advantageous attack. When an enemy misses a melee attack against the slaad, it can use its reaction to make an opposing strength check against the enemy, grappling them if successful.