Rat Colony
Oracle Text
Rat Colony gets +1/+0 for each other Rat you control.
A deck can have any number of cards named Rat Colony.
Card Rulings
4/27/2018 Rat Colony’s last ability lets you ignore only the “four-of” rule. It doesn’t let you ignore format legality.
i.e. Molten Rain, Would be really hard to specify destroying the "normal" lands without the basic type.
I'm open to more rules and explanation but I can't make sense of this. (especially since they have been doing everything in their power to trim text)
However, since this seems to be a better Relentless Rats (traditionally played in mono-B and 20+ Rats), I'm not sure we will see U splashes.