Pandora's invitation was clear: wear a costume, so the monsters hiding among the guests won't know you're not one of them. Hel, goddess of death, the ruler of helheim, gave it serious thought. The trouble was that she was the scariest thing in the entire castle. So she went with the opposite strategy, that is something cute: an orange pumpkin onesie two sizes too big, complete with a stem hat that wobbled with every step.

The strategy worked. A werewolf complimented her costume and asked where she'd bought it. A zombie held the door open for her, very politely. A ghost tried to haunt her, drifted straight through her sleeve, and came out the other side with icicles hanging off its sheet. In the ballroom, a vampire offered her a cup of punch, and it froze solid in her hand. By the apple-bobbing tub, the water turned into a skating rink before anyone got their face wet. On the grand staircase, a suit of haunted armor clanked after her, all menace, until Hel turned around and stared at it, deadpan. It apologized, then offered her cookies.

Thunder rattled the windows, the portraits whispered, and the giant clock in the hall struck twelve. The lights went out. The "guests" dropped their masks: fangs, claws, glowing eyes. Every monster in the castle surged toward the party.

Then they all stopped dead.

In the middle of the dark hall stood a lone pumpkin. Frost crackled across the marble floor, and a pair of eyes, one grey, one clouded white, stared at them without blinking. Someone whispered, "That's... not a costume."

"Trick or treat," said Hel flatly.

The monsters dug into their pockets and handed over every last piece of candy. The vampire even returned the frozen punch with both hands.

From behind a curtain, Pandora sighed. "I said don't get caught... not don't scare them."

Hel looked down at her bulging bag of candy.

Then she looked at Pandora. "...I got treats."

Pandora stared at her and sighed "Just go home."

Hel went home with a full bag of candy, and refused to take off her stem hat.