I used to play a game called dungeon crawl() in which there where \"mutations\", basically the same as your \"anomalies\" only you could get a random mutation whenever you encountered a mutagen. A mutagen is anying that causes a mutation, like radiation, certain spells, eating certain meat, using certain spells too much, certain potions, etc. Mutations could be anything from -1 dexterity to growing scales on part of your body for +1 ac to the ability to spit poison. of course there was a potion of cure mutation, which cleaned all mutations, but I think slightly more precise, spell based anomaly control would be better. The chance of any particular mutation was ridiculously low, but by level ten, three or four mutations would have built up. the bad ones you just lived with because of the good ones. Were(insert critter here) type mutations/anomalies would not be part of the normal list, but could be triggered by special events(getting bit)