Conductor Construct

Heart Breaker.  The Conductor's impulsive actions are governed by an enormous eldritch heart unearthed in the Foundry.  Whenever the Conductor is stunned, it falls down on all fours and the eldritch heart is exposed to attack.  Unlike the metal body which encases it, the eldritch heart has no resistances and is vulnerable to poison and necrotic damage.  The heart is considered a medium sized entity, and retreats into the metal body when the Conductor is no longer stunned.

Clumsy Fists.  Whenever the Conductor makes a Slam attack, any targets currently grappled by the Conductor take half of the damage inflicted on the Conductor's primary target.  Additionally, if the Conductor takes more than 15 damage from a grappled target, it releases the creature.

Enormity.  Any creatures the Conductor walks over during its normal walking movement must succeed on dexterity saving throws DC 10 or take 1d6 bludgeoning damage.

Multiattack. The Conductor can make two attacks.  One slam attack and one of the following:

• One additional slam attack.
• One kick attack.
• One accordion grab.

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., 1-2 targets. Hit: 15 (3d6 + 6) bludgeoning damage. Targets must be adjacent to one another.

Kick.  Melee Weapon Attack:  +10 to hit, reach 5 ft., 1 target.  Hit: 12 (2d6 + 6) bludgeoning damage.  Target is knocked back 10 ft. and creatures behind target must succeed on a dexterity saving throw DC 13 or take 2d6 bludgeoning damage.

Accordion Grab. Ranged Weapon Attack: +10 to hit, range 45 ft., 1 target. Hit: 5 (1d6 + 3) bludgeoning damage.  Target is grappled and moved to a space adjacent to the Conductor. 

Tantrum (Recharge 5/6).  The Conductor throws a childish tantrum, pounding the ground repeatedly and shaking the depot.  All creatures within the depot must succeed on dexterity saving throws DC 14+ or take 2d8 bludgeoning damage from falling debris and fall prone.  Creatures who succeed this saving throw take half damage and do not fall prone.

Time to Play! (Costs 1 Action).  The Conductor calls his trains into the depot to play.  Roll a d4.  The outcome determines which lane(s) the train(s) will emerge from.

1. The top rail.
2. The middle rail.
3. The bottom rail.
4. Both the top and bottom rails.

Lights will shine on the track(s) where the trains will emerge for one whole round.  Once this round has passed, roll another d4.  This outcome determines how the train(s) will interact during the encounter.  Trains 2 & 3 will chug forward every turn, traversing their entire length each round.

1. The train(s) barrel through the depot at top speed.  Creatures caught in the path must succeed on a dexterity saving throw DC 15+ to avoid the train's impact and take 3d6 bludgeoning damage and fall prone.
2. The train(s) stop in the depot, obstructing vision for one round.  During that round, they unload 1d4 clockwork squirrels equipped with bombs into the depot.  These squirrels have 1 hp, an AC of 10, and share an initiative roll with the Conductor.  They will detonate either as an action or upon death, dealing 1d6 fire damage to all creatures in a 5 ft radius.
3. The train(s) stop and spew purple liquid into the depot.  Players starting their turn in the purple liquid's 15 foot cone must make a wisdom saving throw DC 14+ or take 1d6 psychic damage at the beginning of their turn.
4. Treat as a 1.