He will always be a threat and will demand an answer every game
I could write entire articles covering these intricacies, so this isnt the place to discuss them all
You want to fight Grothama with big creatures like Ghalta, Primal Hunger and Mossbridge Troll to kill it and draw bursts of cards
In addition to Urtet's ability which can be played before combat allowing you to untap and swing with massive Myr creatures, the deck features a number of different anthem and +1/+1 counter effects to pump your board including Master of Etherium, Steel Overseer, Urza Prince of Kroog, Chief of the Foundry, Myr Galvanizer, Tempered Steel, etc
While eminently vulnerable to daddy Masticore, Mother of Runes gave a huge bang for the white buck
Herald of Hoofbeats gives your entire board horsemanship, a wildly fitting mechanic for this precon that effectively renders creatures unblockable by all opponents except for the oldest of veterans