It gives legendary creatures a big buff, and it also gives the legendary spells a cascade effect
The two abilities it has are protection, which gives you protection from everything until your next turn when it enters, and card draw, which causes you to lose life in a roundabout way
In my years of collecting, I often find it better to get the biggest pieces out of the way first and then work on the smaller ones, which is certainly doable if youre collecting the most expensive Sun and Moon cards
With cards like Wakening Suns Avatar being a non-dino board wipe and comically large beasts like Apex Altisaur, this deck is wild right out of the box
For more, check out the Magic Story pages for Amonkhet , Hour of Devastation , War of the Spark , March of the Machine , Aetherdrift , and Tarkir: Dragonstorm