Arco's SV:H Hydrapus Model IV

Bloodthirsty. Hydrapus only recognise one another as allies. Nothing is safe from their fury... everything is an enemy to these monsters.

Biomechanical. Created by a mad genius, these monsters are proof that robots are closer to life than people would be comfortable with. They are primitive thinkers with the ability to artificially reproduce, and with their dangerous reactor core and unknown metallic exterior, these things need the caution one would give to both robots and monsters.

Mechanical Hydra. Created anywhere between 20-100, the limbs of a Hydrapus triple as Heads with a singular eye, Hands with three giant claws and Feet with a large surface area for optimal balance. Each head a different size and all capable of switching roles at any given time. The biggest will always play head while the rest operate as needed. And as the case with the Hydra, chop one head off and one of the others will take its place... though this robotic rip-off doesn't regenerate or double the lost head.

Grapple. The target must succeed on a Str./Dex. saving throw (DC = 13 + Str./Dex. No greater than 19) or it has the Grappled condition. If the target is inanimate, no saving throw is required, and the grapple does not count as an action, however, the Hydrapus gains disadvantage on Scratch and Stomp attacks whilst holding the inanimate target.

Scratch. Natural Attack: +6 to hit, reach 20 ft., 1 target. Hit: 3d8 Slashing damage.

Stomp. Natural Attack: +8 to hit, reach 5 ft., 1 target. Hit: 4d12 Bludgeoning damage. The target must succeed on a Con. saving throw (DC = 11 + Con.) or become Prone.

Throw. Natural Attack: +4 to hit, range 25/100 ft., 2 targets. Hit: For every 10 feet thrown, 1d10 fall damage for thrown target and 1d8 Bludgeoning damage for hit target. This attack is only available when the Hydrapus is armed with a grappled primary target.

Ground Pound. The Hydrapus may slam their weight into the ground, causing a minor local earthquake. The surrounding targets must succeed on a Con. saving throw (DC = 10 + Con.) or become one of the following: (1d4)

1. Incapacitated
2. Prone
3. Stunned
4. Unconscious

This action can only be used if the Hydrapus has not lost any heads and cannot be used more than once.

The Core of the Hydrapus remains the strongest part of the entire structure... but that is by design. Inside lays reactive plasma energy contained to power this beast of a murder machine, a plasma so reactive, in fact, it detonates upon contact to Nitrogen... 

Plasma Detonation (Upon Piercing Core). Only triggers if Nitrogen is present. The Hydrapus is instantly and irrevocably destroyed. A ball of plasma energy erupts from the centre of the Hydrapus Core and expands up to 30ft. Those within range with a Dash Speed of 30ft or Higher may roll a Dex. saving throw (DC = 10 + Dex.) to test their reaction time and escape speed. Those who do not succeed will suffer 4d6 lightning damage (the plasma energy), 2d6 fire damage (blast power), 1d6 thunder damage (soundwave) and 1d6 piercing damage (shrapnel). This detonation ignores resistances and reduces immunities to resistances.