Cube based around -1/-1 and +1/+1 counters, as well as Infect.
I don't believe I can make this a singleton deck, considering how few infect/wither creatures there are total, and how few answers there are to them. (IE more than one Leeches to give white answers to infect).
Will have to work out what synergies there are between the color combos to promote interaction.
Interactions:
White based around +1/+1 counters and lifegain. Possibly Humans/Soldiers
Black has infect
Green has Wither
Red is burn
blue is control and infect