Mark is the creation of the mechanical genius, the gnome and Harper of Hundelstone, Thwip Ironbottom. He's the first construct of his kind to run on organic fuel. Mark is constructed of tempered steel and aluminium, with copper wiring and brass gears, all covered in a fine adamantine mesh "skin" which is enchanted to grow soft fur coverings to create the illusion of making Mark look like a regular flesh and blood dog.

The core of Mark's body houses a miniaturised fire elemental that provides the power for locomotion, and as an added benefit, grants Mark the ability to breathe fire.

Mark bonds to his owner and guards them with his life. Mark's enchanted adamantine skin is self repairing while Mark has more than half his hit point total remaining, allowing him to spend his hit dice to heal while resting. As a construct, curative magic has no effect on Mark, but he can be manually repaired with a DC 20 intelligence (tinker's tools) check and an hour of work. A successful check heals 1d8+2 hit points and costs 1 sp per hit point in material costs. A failed check results in a loss of the materials.