They help win games
This means it does literally nothing at first, but can quickly scale to become incredibly dangerous in the right deck
In that respect, it is similar to Whirlwind Rift , but unlike Cyclone Rift, which is turned by hand, this spell destroys everything
Unlike Hearthstone, which only allows players 30 cards, Legends offers up anywhere from 50 cards, which is the minimum to use a deck, to 70, the max
Ghostly Prison does a great job getting to the late game by making opponents choose between attacking and casting spells and every player wants to cast spells
You get Wildcards by opening boosters, competing in events, and winning games to beat your daily and weekly challenges - so if you're short on Wildcards for the shiny new Arena deck you want to build, the best thing to do is get playing with the decks you already have