Rook Kast was a Mandalorian warrior who was loyal to Darth Maul in the comic series Darth Maul: Son of Dathomir.
This comic series came out in 2014 and was grandfathered into the new Star Wars canon since the series was based on unfilmed scripts from The Clone Wars TV series.
In the series Kast, along with fellow Mandalorian Gar Saxon, broke Maul out of prison and took him to the Shadow Collective base on Zanbar. From there Maul, more Mandalorians, Mother Talzin, and a whole bunch of Nightbrothers come face to face with Count Dooku, General Grievous, and Darth Sidious. Plus, Kenobi and Tiplee show up – there’s a lot going on – and this comic series is absolutely worth checking out.
Kast appeared in all four issues of Son of Dathomir and her appearance was reportedly an inspiration for Sabine Wren years later.