To quote something BobCamel said to me when I first submitted an idea.
'Oh great, another person flouting the "Magic the Gathering" vocabulary and ideas which are like a cancer destroying this game' (more or less).
As pointed out, creatures are extremely valuable in this game - on average you have to spend twice as much quanta to get rid of a creature to remove it outright. Obvious alternatives are Freeze and Rewind which only then provide a temporary solution. Other options at card control are Otyugh, Antimatter and Liquid Shadow. But without explaining the mechanics of a card game in too much detail: the more cards you have, the slower and therefore weaker your deck becomes.
While some sort of global creature control card is needed, we already have Firestorm, 3 Damage to all enemy creatures costing 7 Quanta (5 Upgraded). To have a card which removes ALL creatures from the game (presumably burrowed and immortal ones also) would have to cost a lot more than the 7 for Firestorm.
As for Discarding hands... this could potentially cripple the game-play entirely, depending on how it was implemented. Do the cards return to the players deck? Or are they removed from the game entirely? Either way, this is another extremely powerful tool and should be most definitely reserved to another card.
And finally, as for the 20 damage component. Unstable Gas will be a much cheaper alternative to this, see the In Development section (link is beneath the game itself).
So in summary. Like your Ark of Truth, this card will be better broken down into its core parts and made into two cards.
1. Judgement Day:
Cost 15 Quanta - maybe Fire or Light
Ability: Remove all creatures from play (maybe not kill them, but just peacefully remove them from play to stop Bonewall/Boneyard abuse)
2. Second Chance
Cost 7 Quanta - Maybe Time or Light
Ability: Each player discards all of his cards (back to the deck?) and draws an equal number of cards that he or she had previously.
