Awakened Skyclave showing up does indeed trigger landfall! It merely isn't a land while outside of play so that casting it using the stack (meaning your opponent has an opportunity to counter it, among other things.) The relevant ruling can be seen highlighted here.

You will have to provide the appropriate colours when playing a creature with Illusionary Mask. You're playing it facedown so your opponent won't know for sure if you did until it's flipped, but the Mask requires you pay the regular cost of the creature PLUS any amount of extra mana you want to make what it is less obvious.

Fun and solid build, but even keeping its budget in mind, I think you have a couple weak links that could stand to be improved!

Being only one mana is indeed an asset for the elves, but I think Leaden Myr is underperforming - it being an artifact is doing you no good. You might prefer something like Ilysian Caryatid or Whisperer of the Wilds instead, since they're still mana dorks for two but they kick into high gear once you have a Daemogoth out. Wose Pathfinder could also be interesting as having something to do with your mana once you have a big guy out in the late game.

Speaking of, you'll definitely want some more Trample in the mix! An 11/10 is impressive, but it can get blocked by squirrel tokens all day long; three Fists of Ironwood isn't quite enough. Your instants could probably stand to be improved, since as it stands, they're a little... plain. In their place you might like Massive Might (ensuring that necessary trample) or Gaea's Gift (which can be used to protect them from removal!) Also, if it's within the budget, four of Rancor would be just lovely.