But the real payoff is that you can pay 10 life once each turn to untap all lands you control
Rather than being primarily about reprinting expensive cards, the Challenger Decks are designed to give players decks that are at least Friday Night Magicplayable right out of the box and, ideally, legitimate top-tier Standard decks after a handful of upgrades
Filter lands are great in multicolored decks that want to ensure they have access to the right colors of mana at all times
A staple in multiple formats, Cryptic Command is one of the strongest blue spells around
While splashing removal spells can definitely be correct (either because its convenient or sorely needed), splashing game-winning cards tends to be right more often
A lot of balance and care goes into choosing the cost of a card, more than I can express here, but looking for similar effects on existing Magic cards can give you an idea of a fair costfor example, a ramp spell that puts two lands into play ought to cost 4 mana, per Explosive Vegetation