Activate only as a sorcery and only if you've cast an instant or sorcery spell this turn
All of that for three mana is a solid deal
These force your opponent to discard a card from their hand, and while this might not appear all that powerful at first glance, repeatedly forcing your opponent to discard cards or being able to choose a specific card from your opponent's makes discard effects worthwhile
Note that you draw the card on attack, so you can draw into an answer such as a Fog effect, bounce spell, or something similar if you want to stop the attack
Basically, each Jumpstart booster is based on a theme, and if you combine two of these packs together, youll have everything you need to play
You get to attack relentlessly because your creatures won't take damage, and in my experience, when your whole team is menacing, several get through unblocked