Naganti Vassa is a renowned scientist whose research on transformation magic helped that field develop from dangerous and unstable to something reliable enough for many mages to use. Vassa's six arms were a result of her own research; they were a bold experiment performed when she was young, but one she got to work perfectly. Now, her students span the globe and work closely with the Adventurers' Guild to provide their services as medics and as body modification experts. It's still expensive to get done, and fully becoming used to a new body can take weeks, but the results are always just what you asked for.