Mutavault is the cheapest to activate, even if the changeling aspect is not relevant
New to the set are the terms Spacecraft and Station - Spacecraft is a new Artifact subtype, Planet is a new non-basic land subtype, and Station is an activated ability that Spacecraft and some Planets have that help them turn into Creatures
So if you love swinging a 21/21 after casting a bunch of spells, I highly recommend Veyran, Voice of Duality
Its use of vibrant neon colors helps each element of the card pop, and the environmental elements like the purple and green magical smoke, or the gleaming gold of the dead legionnaires equipment are beautifully textured
On top of that, it gets the buff from other spirit lords that are part of the strategy
I still really like Boros as a guild, and I believe Aurelia is very good, but there may not be room to play many copies due to the fierce competition