Canoness-Errant Setheno

Canoness-Errant Setheno, also known as "the Gorgon" was the fourteenth and last Canoness of the Order of the Piercing Thorn, an Order Militant of the Adeptus Sororitas. Despite the fact her order was wiped out (by her own hand, no less) she still roams the galaxy kicking ass and taking names in the God-Emperor's name.

The fall of the Order of the Piercing Thorn

Very little is known about her before the events that befell upon her order. Once a very prestigious and powerful order, the Piercing Thorn claimed many victories over the enemies of Man. Leading the Order, Setheno gained notoriety fast for her bravery and tenacity in battle, and some even claimed she would eventually become the Abbess Sanctorum of the Convent Prioris on Terra (and becoming a member of the High Lords of Terra is no small feat).

Then, something happened. And I mean something, because nobody knows for sure what exactly made her react the way she did. According to some rumours, she uncovered some sort of taint on her order, and she flipped out. Bad. Very bad. Inquisitor levels of bad. She demanded the inmediate destruction of her order, she gathered all of the other Sisters of Battle from other congregations she could find and personally anihilated the Piercing Thorn, leaving nothing behind: every novice was slaughtered, every prioress gutted, every building demolished, the Order's fortress was bombed and burnt to the ground, the land was salted... The Piercing Thorn was no more, and Setheno became its only survivor.

After that happy incident, she refused to join another order, taking the title of Canoness-Errant, a position that she basically made up, but after what she had done noone was going to argue with it. With the massive authority her position brought (not to mention all the shit your pants fear she could cause to everyone that had heard her story) she went around the galaxy fighting the enemies of the Imperium.

Setheno around the galaxy

Canoness-Errant Setheno has been very active since the destruction of her order. In particular, she has been multiple times in Armageddon, becoming acquaintances with Comissar Yarrick during the 2nd War of Armageddon. She has also been known for intimidating botha Space Marine chapter and an Inquisitor into following her orders, despite the fact they both have way more de facto authority than any single sororitas. This goes to show that there's nothing you can't do if you have a scary enough reputation behind you.