I recall reading on the net that there's a Patron Saint of Assassins, believe it or not.
Unfortunately, if there is a real-life one, I can't recall who it was....
In
ADVANCED DUNGEONS & DRAGONS (um, please excuse me, I meant "that
other game"
), one Patron Saint of Thieves and Assassins was "Gygar, the God of Thievery and Luck"; another one was "Sicalon", described as "...[t]he Lord of Shadows and Darkness. He is the patron of thieves, spies, assassins, and those who seek personal gain and power through intrigue and deception."...
Another is Grim, "The Dark One", a/k/a "The Poisoner", "The Assassin", "Soulstealer", or "Plaguebringer". Like Gygar, he is a patron of assassins and thieves.
Their counterpart in
AD&D's "Underdark" is Chemelosian, described as "...the patron of assassins, poisoners, necromancers, conspirators, and those who kill for gain...". Apparently, he has some basis in Norse mythology, because one of his subordinates is Fafnir ("The Wyrm"), the Dwarf-turned-Dragon who is "... worshipped by thieves, dark Dwarves, and those who have given themselves over to their desire for wealth...".
--Foreigner