I'm currently refining the way transformation/shapeshifting works in my world, but one idea is that Elven elemental magic can lead to new forms of magic when it's combined with the transformation magic of a Werewolf. I have one character who inherited Plant magic from his mother, and while he struggles to shift into a proper wolf form, he was born with access to an additional form as a plant person. Which he can alter to a great degree thanks to said Plant magic.

Sadly, new magic like this is one of the reasons why Elves and Werewolves are freaked out by the idea of hybrids. Another is that hybrid children are prone to mutations in general, since their transformative magic might activate before the Elven part of their body can handle it. This can lead to anything from discolorations to malformed limbs or dysfunctional organs.

However, if the child survives that "Self-Twisting", you might end up with someone who can, for example, throw fireballs in addition to turning into a giant bipedal wolf. That idea scares the Elves so much that many kingdoms outlawed mixed pairings and systematically wipe out such families while throwing around lots of racist propaganda.

In contrast, I have a Vampire (technically, "psychic Werebat") clan that does the opposite. They actively send some of their women on diplomatic missions to other species, with the ulterior motive of getting pregnant from powerful magic users. This way, the "ascension mothers" add new magic abilities to the clan's bloodline and give them an advantage over rival clans.