If the target creature is an illegal target as Hydaelyn, the Mothercrystal's last ability tries to resolve, it won't resolve and none of its effects will happen
With a good discard outlet, you're three turns away from Tecutlan, the Searing Rift which uses discover to give you essentially two spells for one
Sure, actual Sneak Attack costs five total mana to snap down an Emrakul, the Aeons Torn where Purphoros costs eight for the first effect and cant cheat in Eldrazi, but if youre putting in something that costs eight or so, its best to think of Purphoros as upfront investment to ramp into a haste threat, much like a Circuitous Route if Circuitous Route also could be a 7/6
Starting last year with Avatar: The Last Airbender , the Jumpstart series is now closely tied to Universes Beyond sets
If you choose to shuffle a graveyard into a library and put a nonland permanent on top, you can even get rid of that permanent in the long-term