Not quite finished with the Iron Gods Adventure Path yet. I ended up modifying some of the random encounters taking inspiration from the original Expedition to the Barrier Peaks. Pris was actually one of the first creatures I converted to 5e as the first thing I converted was Expedition to the Barrier Peaks.
Medium Construct (robot), chaotic evil
Armour Class 18 (synth chassis)
Hit Points 180 (19d10 + 76)
Speed 30 ft.
STR 21 (+5) DEX 18 (+4) CON 18 (+4)
INT 10 (+0) WIS 13 (+1) CHA 20 (+5)
Saving Throws DEX +7, CON +5, WIS +4
Saving Throws Dex +7, Con +9, Wis +7, Cha +9
Skills Perception +4, Stealth +10
Senses darkvision 120ft., passive Perception 14
Challenge 14 (11,500 XP)
Gift of the Machine God. As a creature of technology Pris is immune to disease, poison and psychic damage. It cannot be charmed, frightened, parlayed, petrified, stunned, exhausted or put to sleep. It does not need to sleep, eat or breathe.
Nanite Surge. Pris may gain advantage on one d20 roll per day. Her “tattoos” glow when she uses this ability.
Multiattack. Pris may make three attacks. She may use Static if available.
Vibroblade. Melee Weapon Attack: +10 to hit, reach 10ft., one target.
Hit: 12 (2d6 + 5) piercing damage plus 10 (3d6) force damage. Scores a critical hit on a 19 or 20.
Autopistol. Ranged Weapon Attack: +9 to hit, range 120 ft ., one target.
Hit: 10 (2d4 + 4) piercing damage plus 10 (3d6) ballistic (force/bludgeoning) damage. On a critical hit the bullet continues on to the next target in a line up to 120 ft.
Static (1/Day). Pris’ damage has inadvertently gifted her with a new ability. Once per day Pris releases an electronic wail consisting of electronic feedback. All other creatures within 30 feet of her that can hear her must make a DC 17 Constitution saving throw. On a failure, a creature takes 20 (6d6) thunder damage and are deafened, half damage on a success and are not deafened. A save ends the deafened condition.
Static Wail. When Pris has lost half of its hit points it immediately uses Static. The ability automatically recharges if already used.
Parry. Pris adds 3 to its AC against one melee attack that would hit it. To do so, Pris must see the attacker and be wielding a melee weapon.
Bolt pistol and vibro-katana.
If the characters somehow interact with Pris the basic idea:
The synthetic stares blankly, buzzing and ticking. In a different voice from before, she speaks: “Mutagenic infection of extraterrestrial nature. Biosafety protocols breached. Subjects quarantined in Class Five-stasis facility. Quarantined… Quarantined.” The synthetic clicks loudly. “Stasis breached. Subjects released.”
She smiles. “Now the children will be disciplined…”