Surprise. The assassin is a lady assassin.
(There were a very obscure hint the first time she appeared in the comic)

If you know Skaven lore that will raise eye brow. And if you don't: Female Skaven end up as breeding machine (Called Brood mother) by being heavily drugged continuously.
But i always liked the idea of female skaven managing to (rarely) escape and hide, so here she go.

When young, she escaped her fate thanks to an under dosage, fighting back her "assailant", being beaten till they thought she was dead, thrown into a meat pile which she escaped from by stabbing whoever came by after regaining consciousness, and since then learned to steal food and stab whoever caught her, before turning sneaky-stabbing into her job.
And nobody know about her real identity. At least, nobody alive so far.

The Assassin was this March's choice by Patreon supporters:
https://www.patreon.com/Corrsk