Both are skill lines.

Vampirism: Always active but comes in stages 1-4, the longer you go without "feeding" the higher stage you progress to. As you progress, you lose health regen (doesn't really matter) and take more fire damage (also not too big of a deal) but you gain access to some of the better passives in the vampire skill line (more regens, no movement speed penalty in sneak). There is an ultimate called batswarm and two abilities which can be pretty useful. Both stam and mag specs benefit from being a vampire so from a practical standpoint it's 100% worth it imo, the only downside is it's sort of ugly :lol:.

Werewolf: Only active as an ultimate, but for having it slotted you gain stamina regen. In werewolf form, you take more poison damage and are not able to roll dodge but you're tankier and have higher weapon damage. You'll have access to five werewolf abilities to use. All in all I would say it's more of a RP thing, but you can make a few decent builds in pvp that involve ww and some guilds run all ww in trials for fun. One thing to note is to transform into a ww cost a decent amount of ultimate and it isn't a toggle sort of thing-it is timed so if you're a solo ww it will run out and you'll have to build ultimate again. If you group with others in ww then you can maintain ww for much longer periods. WW is in general most beneficial to stam specs.
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