The Speed Demon, Max Speed mechanic aside, is a pretty traditional black Demon in MTG terms
For example, if you sacrifice a 3/3 creature to cast Fling and then copy it with the ability granted by Dual Casting, the copy of Fling will also deal 3 damage to its target.
(Some of them would take up more room than we have in the text box by themselves, but you probably won't control that many lands.) In case you do end up with more than 31 lands, the remaining prime numbers below 100 are 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, and 97
Can I use any Pokmon card to play
In the meantime, they can keep milling cards until you find one, or you could try milling your opponents with something like Psychic Corrosion to see if you can find a legendary among them
Its one reason the light test can work: cheap cardstock cant replicate the layered structure of real MTG cards