Big Daddy

Acid Absorption. Whenever the golem is subjected to acid damage, it takes no damage and instead regains a number of hit points equal to the acid damage dealt.

Berserk. Whenever the Big Daddy starts its turn with 60 hit points or fewer, roll a d6. On a 6, the golem goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see. If no creature is near enough to move to and attack, the golem attacks an object, with preference for an object smaller than itself. Once the golem goes berserk, it continues to do so until it is destroyed or regains all its hit points.

EVE reserves (3/Day). Small reserves of EVE within the Big Daddy armor activate to restore 2d8 + 2 hit points to itself or to one creature within 5 feet of it.

Immutable Form. The Big Daddy is immune to any spell or effect that would alter its form.

Adam Siphon. If a Little Sister is within 30 ft. of the Big Daddy, it can use an action to siphon Adam from the Little Sister, healing itself for 30 hit points.

Plasmid Enhancement. The Big Daddy can activate a plasmid that enhances its abilities for 1 minute. While the plasmid is active, the Big Daddy gains advantage on all attack rolls and saving throws. Additionally, it can use an action to release a burst of electricity that arcs out to all creatures within 10 ft. Each creature in within 10 ft. makes a DC 15 Dexterity saving throw , taking 4d6 Lightning damage on a failed save or half as much damage on a successful one.

Multiattack. The Big Daddy makes two attacks.

Drill Weapon. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 6) piercing damage.

Grenade Launcher. Ranged Weapon Attack: +8 to hit, range 60/160 ft., one target. Hit: 20 (4d6 + 6) fire damage. Each creature in a 10-foot-radius Sphere centered on that point makes a DC 15 Dexterity saving throw, taking 4d6+6 Fire damage on a failed save or half as much damage on a successful one.

Haste (Recharge 5–6).  Until the end of its next turn, the Big Daddy magically gains a +2 bonus to its AC, has advantage on Dexterity saving throws, and can use its slam attack as a bonus action.

Drill Rush (Recharge 5–6). The monster rushes forward in a straight line for 20 ft. Each creature in the Line makes a DC 17 Dexterity saving throw, taking 2d6 Bludgeoning damage on a failed save or no damaged and not knocked prone on success.

Protect. If a Little Sister within 30 ft. of the Big Daddy is attacked, the Big Daddy can use its reaction to move to the Little Sister's location and take the attack's damage instead.