In the past, when I have played an Ent-based deck, I find myself struggling in the early game (especially in solo) and wishing I could just skip to the late game, when my table is an Ent powerhouse. However, by then, the game is usually over, whether I won by scraping by with a few Ent allies or lost by lack of character support. However with Gríma, you can dish out allies by crazy, and because I can get out at least five Ents by round three, this is my favorite Ent deck to play.
The objective is pretty simple: play as many Ents as possible and kill stuff, as well as provide a substantial amount of , which this deck can do admirably. If you want to have the best play experience, mulligan for Treebeard. This is especially important in this deck because you can play him round 1, which means round 2, you can really get starting playing Ent cards. Just with Gríma's ability, this is amazing as Ent are already under-cost for their stats, but with Keys of Orthanc, this is insane. I usually chuck it on Gríma mainly because its thematic but it can also go on Aragorn as well. With this attachment, you can get out the Ents for basically 2 less, if you're getting back the resource(s) you spent with Gríma. If you're running out of Ents or cards in general, play Entmoot and some card draw events to replenish your stock of war machines. In the early game, this deck is manageable. In the middle game, this deck is amazing. In the late game, this deck is our of control. The highlight was when I had one or more copy of every ally in my deck on the table with 3 Booming Ents (all with 7 or 8 attack).
NOTE: Derndingle Warrior and Leaflock are not currently in my card pool, but they would be a great addition to this deck.