Elden Ring is a game that sprung from the mind of Hidetaki Miyazaki and the fine folks at FromSoftware, so you should always expect something awful to happen to you at any given moment. Walking in the wrong direction after coming out of the tutorial area can lead to you getting walloped by the Tree Sentinel. Simply hugging a woman can have dire consequences. And now it's been discovered that there's even an NPC who will steal runes - Elden Ring's version of souls - from you after you die, which may make them the biggest criminal in Soulslike history.
While you make your way to Stormveil Castle, you may come across a character named Gatekeeper Gostoc. He'll advise you not to enter the castle through the main gate and instead take a safer side path. He also acts as a merchant and sells you various items and crafting materials. Overall, nothing too out of the ordinary when it comes to NPCs within a FromSoftware title.
Most players would never suspect Gatekeeper Gostoc of being a terrible person - unless you happen to enter a certain room containing a Rusty Key - but we now know the full extent of his crimes. When you die and your runes are left on the ground, you may notice that the amount of them seems a bit off when you retrieve them. That's because this jerk swoops in after you're dead and steals 10% of them.
This discovery was made by a user in the Elden Ring subreddit. They found out that every time you drop your runes in Stormveil, this NPC will take some for themselves. The amount they take is just enough of a small number that you may not even realize that you're being robbed. 10% may not seem like all that much, but losing that amount of runes could prevent you from getting an extra level or upgrade that you want. And for that, Gostoc must pay.
If you want to stop Gostoc from pinching runes from you, you can kill him and receive an item called a Bell Bearing. You can hand that over to the Twin Maiden Husks at the Roundtable Hold, and you'll then be able to buy anything that Gostoc was selling from them. In addition to that, he'll also drop all of the runes that he stole from you upon his demise.
It's usually not a good idea to kill NPCs in a Soulslike game, but a special exception can be made in the case of Gatekeeper Gostoc. No one steals my runes and gets away unstabbed.