Mutavault will receive a +1/+1 counter only if it was a creature during the resolution of the last ability of Leyline of Abundance
The zero ability casually gives you three colorless mana - Combine this with the second part of the static ability, and any cheap, colorless spell (Expedition Map) is a removal spell
Sure, we have to attack to get the card draw trigger, but its a 6/6 flyer with ward 2
Back with Magic: The Gathering was young, Wizards of the Coast produced its first of several artifact-based sets and introduced us to the Brothers War, a planet and eventually planar conflict between Mishra and Urza
You are getting a ton of value for your seven mana, as you can exile your opponents best creature while putting a rather large threat in play
Fortunately usually Temur players dont play more than one or two copies