Magic Resistance- The acid symbiote has advantage on all saving throws against spells and other magical effects.

Magic Weapons- The acid symbiotes attacks are magical.

Acidic Surface- When another creature comes into contact with the acid symbiote, the creature take 2d8 acid damage at the beginning it the acid symbiote's turn. If a non-magical weapon comes into contact with the acid symbiote, it starts to dissolve, roll a d4 to see how badly it dissolves, a 1 being not bad at all, and a 4 being unusable.

Acidic Blood- The body of an elemental is fused with the acid symbiote, whenever the acid symbiote takes damage from anything besides a spell, acidic blood shoots out in a 30 foot cone, any creature in that cone must succeed on a DC 18 Dexterity saving throw or take 4d8 acid damage on a fail, half as much on a success. 

Innate Spellcasting- The acid symbiote has basic innate spellcasting, dependent on the type of elemental housed within.

At will- acid splash

Multiattack- The acid symbiote makes three attacks, two with its claws, and one with its acid shot.

Acid Shot- Ranged Weapon Attack: +8 to hit, range 10/30 ft., one target. On hit: 3d8+4 acid damage. 

Acid Claws- Melee Weapon Attack: +10 to hit, reach 5 ft., one target. On hit: 4d8+6 acid damage. 

Pin- The acid symbiote can use its action to pin a target. The target must make a contested Athletics check against the acid symbiote's athletic check, if the acid symbiote succeeds, both the target and the acid symbiote are restrained. The creature can attempt a contested Athletics check at the end of their turn, ending the effect on a success.

Acidic Drowning- If the acid symbiote succeeds on its pin at can immediately use its bonus action to dump copious amounts of its acidic blood on the target, causing 4d8 acid damage, doing this will give the target advantage on any checks it makes to try and break out of the pin. 

Acidic Burst- When an acid symbiote dies, it explodes on its turn in initiative. The acidic contents of the construct cover a 20 foot radius, making the area very deadly. Any creature must succeed a DC 18 Dexterity saving throw, taking 2d8 acid damage on a fail, half as much on a success.