Kataphron Battle Servitors
Kataphron Battle Servitors are Combat Servitors given an upgrade. They act as elite shock troops meant for dealing with heavier and tougher opponents that their smaller cousins couldn't do. Due to the opponents they face, Kataphron Battle Servitors are far, far larger and heavier, requiring anti-tank weapons to take them down and even that doesn't work all the time.
Their increased size due to the heavier armor has rendered their already augmented human legs as too impractical and more vulnerable to wear and tear, instead opting for giant tank treads. While this may severely reduce its agility, speed and overall flexibility, the treads do enable more stability, durability and adaptability that normal human legs couldn't survive even when augmented.
Completely severed from all emotion and independent thought, these machines are little more than a living weapon controlled by Tech Priests. There are two types of Kataphrons which the Mechanicus uses.
A funny thing to note about the Kataphrons is their weapon choice for each role is an inverse to that of the Skitarii. For example, the long range Skitarii Rangers have Arc Rifles as their best special weapon, while the short ranged Vanguards use Plasma Calivers. Meanwhile the long range Kataphron Destroyers use Plasma Culverins and the short range Breachers use Heavy Arc Rifles.
Kataphron Breachers are used by the Mechanicum as a living shield and battering ram, smashing apart enemy lines and formations. They are quite deadly in close quarters combat, equipped with a large array of weapons that can include Arc Rifles, Torsion Cannons, Arc Claws and Hydraulic Claws. These machines are also equipped with a Kataphron Breacherplate, powerful cybernetically-enhanced titanium-laced metal and plastisteel that turns aside blades and bullets alike.
In terms of tabletop rules. The Kataphron boasts a MEQ-equivalent armor save, an Arc Rifle that does d6 damage against vehicles , and a CCW that also does extra damage against vehicles. It can alternately switch that CCW for a different one that is Sx2 AP-1 D3 damage but suffers -1 to hit rolls or replace its gun for a Torsion Cannon- a single shot S8 AP-4 weapon that does d6 damage.
As it names implies, Breachers mutilate fortifications and even tanks with relative ease Unfortunately not any more, they're expensive as hell, Arc weapons got nerfed into the ground, and torsion cannons are too expensive to ever justify. If you really want to take them either stick with Arc weapons which are relatively cheap. On the plus side, they got a price decrease in chapter approved, so... yay?
Update: Turns out that t5 3 wound models that are also infantry are really good! With easy access to -1 to hit, 1+ for ALL saving throws you can easily make 12 of these be 36 wounds at -1 to hit with 1+ and 4++. Just remember to take an inquisitor because literal robots still have godawful leadership for some reason.
You want to fuck up that column of Terminators and Battlesuits, you want to wipe the smile off that grinning Ultrasmurf Fanboy and Weeaboo Fuckers. You need the Kataphron Destroyers. Kataphron Destroyers are used as heavy weapon platforms by the Mechanicum, ensuring that nothing will be left of their enemies but molten sludge. Thus they are equipped with a large amount of heavy weaponry that includes Grav-Cannons, Phosphor Blasters, Plasma Culverins, and Heavy Flamers to completely eviscerate enemy armor. For protection, these machines are equipped with Kataphron Demiplates, lighter armour that allows better cooling of its heavy weaponry. Nonetheless this cybernetically enhanced heavy steel provides a great deal of protection.
On tabletop, Kataphron Destroyers by default start with a Plasma Culverin and a cover-ignoring Phosphor Blaster, but you can switch the Plasma for the Heavy Grav-Cannon and the Phosphor for a Cognis Flamer. Grav has been nerfed heavily as of 8th, it is still decent however due to the sheer volume of fire they put out but now both loadouts are viable since three Plasma Culverins firing a total of 3d6 S7 AP-3 shots is nothing to sneeze at.