If you reduce your opponents Pokmons HP to zero, it is Knocked Out, then discarded (along with all attached cards) and you draw a Prize Card, which you add to your hand
The goal is to rush in with this for a lot of damage, before casting it later on - if the game is still going by then
Don't be afraid to use cards like Bubble Snare, Into the Roil, and Inscription of Insight aggressively in the early game, even unkicked
With Tarkir: Dragonstorm prerelease events beginning on Friday, April 4th, it is entirely plausible that these were sent under the pretense that they were Tarkir prerelease kits
If you see multiple items that you may want to bundle, please feel free to reach out