Vampire Survivors: What Does Luck Do?

gamerant.com:

There are several stats in Vampire Survivors, and most of them are focused around a character's survivability and efficacy in combat. There are some stats that do not fit neatly into either of those categories, though, and one of them is Luck. For those players that would like to learn more about the Luck stat in Vampire Survivors, full details on its functionality can be found in this guide.

Luck impacts a number of aspects of this game, the first of which manifests during the weapon and accessory selection that occurs every time that a player levels up. More specifically, Luck makes it possible for an additional fourth choice to be made available during each of those selections, giving fans a better chance at seeing the items that they are interested in. While this may not seem like a significant benefit, it does make it easier to evolve weapons in Vampire Survivors.

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Increasing Luck also improves the chances of receiving an item in Vampire Survivors, like a Rosary, NFT, or Orologion, from destroying light sources, while also raising the chances of receiving three-item chests from rare enemies. Undoubtedly, these effects are extremely desirable and have the potential to have a major impact on the success of a run. That said, fans must sacrifice some level-up selections and inventory slots if they want to increase their Luck significantly, and it may not be feasible to do so in most runs.

Finally, Luck decreases the chances that a negative event, such as a swarm of bats or ring of plants, will occur and also increases the likelihood of landing a critical hit. That said, it is important to mention that there are only two weapons capable of critical hits at the time of writing.