Dwarf Fortress.

Someone on Reddit had a play session of roughly ordinary productivity:

The partial skeleton of a kobold thief animated and is now my fortress' guardian....

This is in a "Wilderness Biome" nowhere near any kind of evil. It only attacks goblin invaders/thieves and ignores my dwarves. I'm not even sure if it's moving when a goblin isn't near it.

Is this some kind of awesome bug?

EDIT: My guardian betrayed me... EDIT 2: Necromancers. They found the goblins their kobold insider killed. 10% of the population died before I could react EDIT 3: 25% EDIT 4: 4 Necromancers dead. 3 Hammer Lords tantrumming. 50% dead. Still more undead roaming...how many more necromancers could their possibly be? EDIT 5: 70% dead. Entire squad of Axe Lords is dead. Only 3 of the 10 hammer lords remain. 0/6 sword masters, 1 swordsdorf. All marksdwarves are dead. All speardwarves are dead.

EDIT 6: 12 dwarves remain. The last Hammer Lord is now rampaging in the deepest levels of the fort. His old friends and many of their body parts rampage above. The remaining necromancers have not shown their faces.

EDIT 7: A carpenter has elected himself mayor. He stands alone in his bedroom. The undead howl and pound at his door. An additional undead siege has arrived to make things more FUN. 232 undead await. 1 dwarf is alive.