This is my attempt at a mono-green build for Standard. It relies on putting many creatures on the board and enabling Rhonas's Monument to pump them and get them bigger while making them less-costed. Enjoy!
MAIN BOARD
Creatures
Kumena's Speaker is a 1/1 merfolk that costs , though it has the potential to become bigger if another merfolk is on the battlefield. I know it typically goes better in a Simic deck because an Island will also pump it up, but we're running 16 merfolk in this deck. It'll be a 2/2 more often than it isn't.
Merfolk Branchwalker is just a great card in green decks. It costs for a 2/1, but it has explore which basically means it'll either draw you a land or become a 3/2. Upside, with the monument in play it'll only cost for a 2/1 draw a card or a 3/2.
Deeproot Warrior is the other 2-drop in the deck and I actually think it's about as good as the Branchwalker. It's a 2/2 for 2 (pretty vanilla), but the upside is that it gets bigger when blocked. Pump him with the monument and suddenly you have a 4/4 trample or a 5/5 trample if he's blocked, which is pretty hard to deal with, barring removal.
Vineshaper Mystic is the pseudo-Lady of the deck since she pumps all the merfolk before her. Kumena's Speaker is now a 3/3. The Brachwalker is either a 3/2 or 4/3. The Deeproot Warrior is now a 3/3 or a 4/4 if blocked. The Vineshaper even pumps herself making her a 2/4 which is a lot harder to remove with removal. She avoids Fatal Push unless your opponent lost a permanent, Essence Extraction no longer kills her, Shock and Lightning Strike do nothing. She's just great for the early creatures in your deck. She also only costs if you happen to have a monument in play!
Ripjaw Raptor is a solid creature for this deck. A 4/5 body with a CMC of 4 that also draws you a card if it's damaged is just excellent. The raptor may be the best creature in the deck. It dies to a revolted Fatal Push and a Vraska's Contempt, but we have ways of countering those cards. Plus it plays nice on curve if you played a monument on turn three as now it only costs and you can use that other mana to protect it assuming you have Blossoming Defense in hand.
Verdurous Gearhulk is just a best in this deck. It has the potential to pump four of your creatures or pump itself up to anywhere between a 5/5 to an 8/8 with trample. Plus, it gets cheaper to cast with a monument on board.
Rhonas the Indomitable is a fickle god. He only likes joining the fray when you have other huge creatures on the battlefield. Apparently, he really likes his beefcakes... They should have just called him Mac. I applaud you if you got that reference. Anyways, Rhonas is a 5/5 indestructible, deathtouch god with the ability to give another creature +2/+0 and trample until EOT for . Notice, he can't pump himself and take advantage of his deathtouch. You can, however, pump him using his monument making him a 7/7 trample, deathtouch, indestructible god... Whew! Talk about being a monster!
Armorcraft Judge is here as a 1-of because sometimes you'll have creatures with counters on them and when he ETB, he'll draw you cards for each other creature with a counter on them. Having a 3/3 body isn't bad, either.
Spells
Rhonas's Monument is one of the greatest things about this deck. It only costs and it makes all you green creatures (which in this case is ALL of your creatures) cost less to cast. Then, whenever a creature is cast you get to pump another creature on board with +2/+2 and trample. It's just great!
Lifecrafter's Bestiary is here to help filter through your deck and draw you cards if pay an extra mana when casting creatures, which will especially be helpful if you have a monument in play since your creatures will cost one less mana anyways.
Blossoming Defense is here because we don't like removal. Our creatures are very suspectible to removal and we want to keep them around for as long as possible! It also helps that this spell adds +2/+2. It makes for a great combat trick sometimes.
Heroic Intervention is also here for removal, however this spell gives hexproof to EVERYTHING on board so you can protect your monument from a Cast Out and it makes your permanents indestructible which is great against your opponent's Fumigate or Bontu's Last Reckoning. Playing 4-of for both of these spells may seem excessive, but removal is literally everywhere in this Standard season and I like playing green, dammit! I want to protect my guys!
Nissa, Vital Force is here to make a land into a huge 5/5 elemental creature, to bring a creature back from the graveyard and into your hand, or if you ultimate her you can draw a card every time you play a land. Plus, you can ultimate her on the very next turn since she comes in with 5 loyalty counters.
Lands
Hashep Oasis is here to effectively Giant Growth one of your creatures. It's at sorcery speed, but sometimes it'll matter.
Scavenger Grounds is probably the more important desert in the deck. God-Pharoah's Gift decks are still around and with The Scarab God being as popular as it is, it's handy to just exile all graveyards. More often than not, you'll probably just sacrifice an oasis to the scavenger grounds.
SIDEBOARD
Prowling Serpopard is here because we like being able to play creatures against control decks. Bring this cat snake out and protect it with your hexproof spells and you'll be able to playu creatures indefinitely. Your opponent's Essence Scatter and Disallow won't even affect you. Of course, you can also play Carnage Tyrant, but I don't have the money for them.
Appetite for the Unnatural is for the God-Pharoah's Gifts, the Cast Outs, the Ixalan's Bindings, the Aethersphere Harvesters, and all the other enchantments/artifacts out there of the format.
Life Goes On is here for your aggro match-ups. For a single mana you can gain 4 life or if a creature died you can gain 8 life. You can also play Aetherspere Harvester here. I might actually try that when I get more money to buy a few of them.
Crook of Condemnation is here once again for The Scarab God and GPG decks. Sometimes you won't always find your Scavenger Grounds in time so having this to exile one card at a time or all graveyards will help.
Nissa, Vital Force and Armorcraft Judge are here in case you need those extra creatures and drawing power. They help in more grindy match-ups.
