Mono Green Landfall relies on cheap mana creatures and a few creatures with activated abilities, and Clarion Conqueror's static ability shuts those down: Llanowar Elves can't tap for mana and Keen-Eyed Curator can't exile cards from graveyards. It does not stop landfall triggers or warp, so Icetill Explorer, Mossborn Hydra and Mightform Harmonizer still work normally. Conqueror is still a 3/3 flyer that blocks and clocks well against their ground creatures. Avatar's Wrath answers a problematic board of attackers like Mossborn Hydra or Keen-Eyed Curator by exiling every creature except the one you choose to target, so point it at your own best creature. The opponent may recast exiled creatures for {2}, but until your next turn they can't cast spells from anywhere other than their hand, so those creatures stay stuck in exile for a turn cycle. Springleaf Drum is low-impact against a deck that doesn't pressure your mana, and it is an artifact whose ability Clarion Conqueror would turn off on your own side. A second one-drop like Zack Fair matters less than beefing up your removal and bodies against their bigger creatures.