Stalker
A monstrosity created by the mechanics to be an elite assassin. Part man, Part golem, it moves with terrifying speed and strikes with awesome power. Possibly a boss.
Stats
Health: 340
Speed: 8 (I know, I know, the speed's very high, but I'm sure you can appreciate why)
Attacks: Perhaps a selection of attacks from golems and assassins?
Resistance: Physical.
Obviously, the stats can be revised.