The Amber and Amethyst deck is for players who like having a lot of characters out at one time, while the Ruby and Emerald deck comes with a dash of control and counter abilities, meant to frustrate opponents as much as possible
Last March of the Ents is a solid newcomer that cant be countered, but costs that little bit more mana (and a lot more cash money)
In sideboards, top picks include Ghost Vacuum, Duress, Negate, Urabrask's Forge, Elspeth's Smite, Pawpatch Formation, Exorcise, and Rest in Peace
Fathomless descent is similar to descend X, but the ability will be dependant on the number of permanent cards currently in your graveyard when the ability is activated (usually as a comes-into-play effect)
The marginal benefits gained from proper phase play add up over the course of a game, a match, and certainly a tournament