Because Helm of Obediences ability only stops milling once it has either milled X cards or a creature, if you have a replacement effect in play that exiles cards when they go to the graveyard, the Helm never sees either of its conditions met, and it just mills the entire library
Or, it can play combo-control
In addition to new Jumpstart Boosters, this Jumpstart release includes five new-to- Magic rare cards from the world of Middle-earth
Delney also gives each creature under their protection evasion, enabling them to avoid being blocked by creatures with power 3 or greater, making swarms of 1/1 and 2/2 tokens into serious threats against most boards
TERMINAL VELOCITY A sneak-attack-like effect that allows a creature or artifact to hit the board, potentially getting some nifty enters ability, an attack, and an explosive exit that could leave the board blank in your favor