Phyrexian Crusader has infect and first strike and proc red and proc white, while the Phyrexian Hydra just needs trample to be a house and, finally, Reaper of Sheoldred fits like it was made for this deck, simply because it does the infect thing and it also has a poison counter tax effect for attacking opponents and as a 2/5 body it can take a bit of damage and then grin as it dishes out some poison counters for you to proliferate
The combo line here is more specific than that of Wall Combo, but its also much faster if you draw your pieces early
This story-driven angle makes the cards artwork particularly cool , significantly raising its collectible appeal
It does require you to exile one of your own creatures, which is certainly a set-up cost, but its one worth paying
There were other card options, and they went out of their way to pick lower power alternatives