Walking through the streets of any festive town over the Christmas season is a truly wonderful experience. Lights glow on lamp-posts and railings, carolers sing on doorsteps and the smell of roast dinners and cinnamon baked goods drifts lovingly through the air.

In Iceland, however, you may notice one thing different than you would in another country.

When looking into windows, one might expect to see families gathered around trees wrapped in tinsel, or pulling crackers at an overladen dinner table. In Iceland, you’re more likely to see the shutters downs and the curtains tightly drawn.

The reason? Well, last night marked the ascent of the creepiest and most threatening Yule Lad thus far… Gluggagægir.

Rather than gift certain households, all of the thirteen Yule Lads—the Icelandic versions of Santa—prefer to wreak havoc over yuletide. They are all criminals and mischievous in one way or another, but Gluggagægir is the one that many Icelanders dread the most.

See Also: Christmas in Iceland 

In English, his name means ‘Window Peeper’. This foul-looking, half-troll creeps up to buildings and looks for a crack in the curtain to stare at those sleeping inside. His modus operandi, however, is not just to petrify those who catch him lurking, but to seek out anything to steal.

Most of his brothers keep to stealing specific items, such as sausages, skyr or leftovers. Gluggagægir, however, has no specific agenda when he reaches his targets; he seeks only the most valuable possessions inside.

In modern times, the Yule Lads have been sanitised as pranksters who leave gifts on window-sills as amends for their naughty behaviour. In this particular case, however, such a concession is not likely to bring any solace.

To find a brand new pair of socks waiting for you in the morning will do little to make up for the fact that Gluggagægir spotted your laptop, iPhone and jewellery, and more likely than not, scampered off with them in the night.