By the way, BGU mana cost is also quite fitting (at least for me), possibly representing Sin's connections to oceans (blue), death (black), and the natural cycle it's strangely bound to (green)
Overall, the deck is very experimental, so I wouldnt put too much stock in Siegebreakers absence there
Theyre really quite good looking for still being closely associated with the default card frame
702.170e: If an effect refers to plotting a card, it means performing the special action associated with a plot ability
Being safe from your own Gibbering Descent, being unassailable with Ensnaring Bridge, having Infernal Tutor be good for once, or murdering someone with an Anthem of Rakdos 10 turns faster than they expected, building around Hellbent has advantages