Those special mobs just spawn during a special ingame time.
Vampires - new moon
Werewolves - fullmoon
Easier is to ask a guild mate who is allready vampire or werewolf, as the mobs are hard to find and some people kill them if they got bitten instead of just running away and out of combat.
Thanks for this informationRAGUNAnoOne wrote: »it is not, vampires have consistent flame weakness and the health regeneration drops with each stage (along with the cost of vamp abilities) and if you are on PC (and on console in 2 days) you will not gain any positive passives apparently unless you slot a vamp ability.
werewolves had constant stam regen buff but it got changed on PC (consoles soon following) so it only works while you slot the ultimate. while transformed you are weak to poison.
also both of them are weak against FG abilities that some guards use (to affect werewolves you need an extra perk) so be careful not to swim to escape as a turned WW or vamp and be extra careful in PvP