Enneracts in Wolcen: Lords of Mayhem are how you unlock new skills. Because the game is class free, allowing you to learn any type of spell or skill that you find, Enneracts are a pretty common drop. You can get them from dead enemies, chests, or corpses that you can find all over the game. Enneracts appear in your Inventory as small books, and to learn them you just right-click on them in the Inventory screen.
All Enneracts will tell you which types of weapons they need in order to be used. Some are melee only, while others require bows or pistols. Some can only be used with catalysts and staves, traditional weapons for magic-wielding wizards. If you don’t think you will be using a particular spell, or find a duplicate Enneract, you can sell them to Demetra at Stormfall for Primordial Affinity, which can be used to level up learned skills.
Demetra will also sell you different Enneracts at different points in the campaign, so it is always a good idea to check what she has in stock. She can have some much sought after Enneracts in stock, and if you have been having bad luck with RNG, it is a great way to get some new skills for your build.
Skills can level up from use in combat, or by using the Primordial Affinity that you can get from Demetra. How you want to play the game will dictate how you use Enneracts. If you plan on sticking with one type of build, you can simply sell the Enneracts you cannot use with your weapons of choice. If you want to keep your options open, it is a good idea to keep the Enneracts in your storage chest, so that you can decide what to do with them later.