The ability to choose between wiping all dragons or everything else lets you break board stalls wide open while leaving your creatures untouched
It turns the graveyard itself into part of the summoning ritual, and thats something that emotionally resonates quite strongly with the source material.
When Sheoldred enters, each opponent sacrifices a nontoken creature or planeswalker of their choice
Blue: Sea Gate Restoration, Rhystic Study (I mean, it has to be listed here), Pull From Tomorrow, Treasure Cruise, etc
Whenever a town has an associated plot battle, that battle will take place in a node slightly off the town, allowing players to prepare, buy new weapons, grind, and take the battle when they themselves are ready