Just a few of things...
1. There are many "dark/corrupted" people in Altera, and we have the Emerald fellows to be the typical hired swords, the Crusade to fight the heretics, occultists, and worshippers of evil gods, we have the Slayers to fight dark creatures/monsters, so I am guessing this will be mostly aimed at the humanoid races, and wrongdoers such as murderers and corrupted nobles?
2. You say in the end the guild will triumph, but surely that will require planning, and - most importantly - permission, from whoever is the target? Also just how many people do you think will actually agree to being killed? Unless, of course, they are to be resurrected by the Sisterhood? And what will this achieve if they do choose to just keep coming back again... and again... and again?