Though based on the mechanics seen in the game released in 2022, Elden Ring Nightreign changes and twists a good number of them so that they can work in its fast-paced, co-op-focused experience. Among the mechanics that have been changed are those that power Armaments, the weapons that all Nightfarers can use in Limveld to fight against the Nightlords and their hordes.
Every Armament in Elden Ring Nightreign, with the exception of the starting Armaments of each character, comes with passive skills. These skills range from simple HP, FP, and Stamina increases to more situational skills, such as abilities that come into effect when conditions are met, such as high or low HP, inflicting certain status ailments to enemies, and so on. As these effects can be extremely beneficial, understanding precisely how they work can make the difference between victory and defeat in a run.
As a general rule, passive skills attached to Armaments are always active, so just having an Armament in your possession will activate the skill, even if you are not actively equipping or using said Armament. The exceptions to this rule are certain passive skills with a small hand icon in the main menu, such as the Add Magic to Weapon skill in the screenshot above. This icon indicates that the passive skill is only active when equipping and using the weapon, and it usually comes attached to skills like HP or FP restoration when hitting enemies.
A big part of the Elden Ring Nightreign experience is to make your character as powerful as possible before Day 3 and the fight against a Nightlord, so filling your Armament slots with weapons that come with useful passive skills should be your priority. As such, you should pick up even Armaments you don’t plan on using to take advantage of these mechanics, and increase your character’s power to survive the Night and all the dangers it brings.

