Nathan once did a deep cover operation as a Lamia, essentially a snake-taur in universe, in order to rescue someone very important to him. The transformation was not pleasant, particularly the gender swap that was involved and the fact he wasn't adequately informed ahead of time of what exactly the operation would entail. He's since had to relive this shape a few times, and it looks like it's happening again right now! That can't be pleasant, or good for the clothing on your lower half.

Drawn by John Fell