Build-a-Bot Engineer

Build-a-Bot Engineer is a Galactic Legendary zombie in the Hearty class. It has 1/4, and costs 2. It says, "When you play a Machine: this gets +1/+1 and Conjures a Machine."

Origins
Build-a-Bot Engineer is based on an Engineer, a person who builds things, and Build-a-Bots, defensive turrets from PvZ:GW2.

With
Stat-wise, this zombie is comparable to Zombot Drone Engineer. Its ability is what makes it shine. Having just one Machine card will allow this to go in an infinite loop, buffing its stats. Hammer is especially good, as the spawned Rivet will also count as playing a Machine. The same goes for Bit & Bolts. Beware, though: If your opponent is a  Guardian hero they could use Doom-Shroom or Shamrocket, and a  Solar could use Lawnmower or Squash.

Against
This zombie is not threatening stat-wise, but can destroy your defenses with its ability. If you are a hybrid hero, you can use Quickdraw Con Man to punish your opponent for card draw, or  Deadly zombies. Otherwise, use your regular hard removal or bouncing.

Trivia

 * It was made for The Enginator (PvZH).
 * It is the second Legendary for said hero.
 * It was also made for the new Machine class.
 * Said class will become a main  Hearty class.
 * It is also GravityWave's first Trick.