This is a really cool blue enchantment that was unique when it was first printed (although we did see Double Down in Outlaws of Thunder Junction )
Theres a lot of ways to break these, like running creatures that create multiple bodies, but having to include these in certain build-arounds holds them back a bit
Notably, opponents can't try to change the cost by removing your Giants and Wizards
Take Faithless Looting, for example: you draw two cards, but you have to discard two, and you used up the Faithless Looting
With a 4 mana cost, this 2/3 creature really rewards you for getting creatures into play, something that green decks tend to like doing anyway
Leovold, Emissary of Trest A common story among the upper ranks, Leovold, Emissary of Trest was an amazing card-draw (for you) and draw-hate (for your foes) Sultai commander until, victim of its own success, it was banned from EDH