Normally it will remain tapped until your next untap step, when it will untap
This card was also very playable in the TCG, and continues to offer a lot of display-ability in a collection
Of course, if you can transform Eddie Brock, you can immediately attack with the menacing, trampling, haste creature and immediate generate card advantage by attacking and sacrificing another creature
Take Equilibrium for example
If a box comes to us and is marked as a "set", we do not check to see if every card is present
It seems that this would be a very effective defense against any targeting, for any action in-game, due to the risk of the active players card being immediately removed from play