Designer Notes: The Ur-Dragon is a great way to play all your dragons early by reducing their cost, while also helping you draw cards and finish out the game once you get to 9 mana
Mind Stone is the most popular of these cards with draw written on them: A mana rock that replaces itself always comes in handy
Tomb of Annihilation doesnt need to go in your deck, and venture into the dungeon effects are plentiful, meaning you can conjure The Atropal almost as an afterthought
As a package of stats with an expensive activated ability, Chameleon Colossus is nothing special, but toss in a random protection ability, and suddenly it looks more appealing
And it's worth it as this magecraft is nasty
If you have been grinding the Standard ladder recently, you know the format has felt a bit solved for months