Warforged Titan, Piston Mark I

Platforms. The warforged titan has two platforms built into its chassis. One Medium or smaller creature can ride on each platform without squeezing. To make a melee attack against a target within 5 feet of the warforged, they must use spears or weapons with reach and the target must be Large or larger.

Siege Monster. The warforged titan deals double damage to objects and structures.

Multiattack. The warforged titan makes two hammerfist attack.

Power Over Speed. The Piston Mark I sacrifices speed for raw power. It's slow movements are predictable, lowering its chance to strike a target directly. The raw power of its blows compensates for this by causing area of effect damage, even when it misses. 

Reverberations. Any missed attacks follow through to the ground causing a shockwave at the point of impact. Creatures within a 5ft radius of the hammerfist target take half damage from the attack. Creatures within a 10ft radius take one quarter of the damage. 

Hammerfist. Melee Weapon Attack: -2 to hit, reach 10 ft., one target. (8d8 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.