Very nice. I see the potential for a 7/7 hexproof double-Strike trampler on turn 3.
Some explosive starts possible for this deck.
A good consideration for
Majestic Myriarch is
Ramunap Hydra. Gives some good attributes and is not too bad itself with some deserts.
Speaking of which, I would suggest putting in some
Shefet Dunes and
Hashep Oasis.
Also just keep in mind,
Majestic Myriarch is vulnrable in the first main phase each turn as it doesn't gain attributes until combat starts.
But the up side of that is you can buff your other creatures in the main phase and
Majestic Myriarch will inherit them.
How about
Legion's Landing? Another way to give
Majestic Myriarch lifelink and create more creatures to increase power and toughness.