Players of Assassin's Creed: Valhalla have found a super-powerful magic bow hidden in a pile of shiny rocks, and they've found it in a way that the developers absolutely did not intend. The secret bow, created by Assassin's Creed's alien space gods, the Isu, is located underneath a pile of rocks. There's some secret path that nobody has quite found yet, but there's also the way where you find the pile of rocks and hit it some and then reload your save and then hit it some more. Here's AC Valhalla Narrative Director Darby McDevitt on the hack:
FYI this is a clever brute force hack, not the “proper” way to get this bow. There is an “in world” way to achieve it. But I suppose this works for an Any% Speedrun. 😎January 24, 2021
The weapon itself is an extremely powerful bow made by the ancient Isu, which is part of the lore of Assassin's Creed that only people who really really care about Assassin's Creed know about. The short version, at least, is that they're godlike aliens that used to rule humanity. So… it's an alien space bow. It's called Nodens' Arc, a reference to the ancient Celtic god associated with things like hunting, healing, and dogs, and equated by the Romans with their god Mars.
The video below, from video creator JorRaptor, explains how the exploit works.