I have noticed that I don't know if there are any magic sets that have a cycle of 4 colour factions, like how Alara/Tarkir have 3 and Ravnica has 2. And so, I introduce:
Plane of power
Sarnas is a plane where 5 factions war for power. Not very unusual, all right, except for the fact that all factions use almost all types of magic. The plane itself is relatively unremarkable, like Ravnica, pre-city.
Some of the factions:
~the Sorlef Foundation (non-green)
~the Fray Millitia (non-black)
~the Kaldos Union! (non-blue)
this will be added to as people make new factions.
What the contest actually is
I would like you to select/make a faction (it can be one that has already been chosen) and make any of the following:
~A leader/champion (only one of each for each faction so you can't make one if someone else has)
~normal cards for the faction ("Guildgates" included)
~a custom mechanic that works with the faction.