For creatures, that usually means you must cast it during a main phase of your turn while the stack is empty
The Majespecter Engine was once so good it had to be hit on the banlist, with Majespecter Unicorn Kirin being banned from play
Aerith Gainsborough, one of the leading heroines from Final Fantasy VII, its spinoffs, and its ongoing trilogy of in-depth remakes, is a shining example
You also have Tato Farmer that can help save any land you want from getting milled, so you do have a backup plan if milling goes poorly
Painlands There are four other pain lands in The Brothers' War to match the mixed set printed in Dominaria United
Pull rate is approximately 1 per 5 boxes making this the most likely significant value hit from any S7R box opening