is For Helm of Obedience the Oracle text reads: "Target opponent puts cards from the top of his or her library into his or her graveyard until a creature card or X cards are put into that graveyard this way, whichever comes first." However, Leyline of the Void states that, "If a card would be put into an opponent's graveyard from anywhere, exile it instead." Because the cards are being exiled and not going to the Graveyard the 'stop' condition in the Helm's text is never met and so you only stop putting cards from the top off your opponent's library into exile when you run out of cards
For a quick overview, Magic can be pretty expensive, especially if you want to play competitively in formats like Legacy or even Modern
It is a poor card if you don't
That's all on card rarities for now, but if you have any more questions about the TCG, why not send us a message in the official Wargamer Discord
Well, mana spells are half the equation of a Storm deck, with the other half being card draw, which our commander transforms burn spells into