You had been an adventurer for a good three years. Halfway through your first year, you met an old magical weapon Smith, who created for you a magical blade after you saved him from a horny monster. The man seemed... wrong, but you ignored it, being new and dumb. The first red flag had been when you walked in on him hammering at it, and asked how it was going.
“Oh, fine, just need to hammer out some kinks.”
“I like feet”, replied the sword.
He cursed and went at the sword. You were obviously... uncomfortable, but trusted the old man to finish the sword properly.
When it came out, the sword could cut any item known to man. Even a diamond plated shields. But there was one problem.
The sword was possessed by the spirit of an extremely sardonic former hero due to the fact that the smith had cooled the blade with the liquid of his blood and built the iron handle from iron in the adventurers blood. The sword, though, only functioned as a blade if the hero felt like it.
Now three years later, the monster who had gone after the smith is coming after you; and the hero doesn’t really seem to give a shit