Go for defense and mana boost until you get a Myr Turbine - then, if you still don't have enough Myrs, keep adding tokens to build an army, either with the Turbine itself,
Myrsmith
or with
Master's Call
.
Don't get rid of your Myr Servitor(s) right away - two of them in the battlefield loops them: while one attacks, the other stays behind, and even if the attacker gets killed, it comes back next turn.
As soon as you can, safely tap your Myrs and get Myr Battlesphere out, along with its small token army. If you have cards like
Myr Galvanizer
and
Tempered Steel
out by now, then you should already have a pretty impressive battalion.
In the meantime, use your Instants to get rid of pesky/strong creatures - exiling them with Dispatch or Path to Exile. And if you still aren't happy, use
Dispense Justice
to slow down an agressive bunch of creatures. If the creature's really strong though, might as well add
Soul's Grace
to the deck, to boost up your life points.
Hope you like this little concoction I brewed up! I always wanted a Myr Tribal, so I guess I'm pretty darned pleased about this one. It can get silly really quick if you're lucky enough, but even if you aren't, when it finally starts building up, it's like a... MYR AVALANCHE!
