The second set in the Time Spiral block, Planar Chaos features 165 cards with randomly-inserted premium cards. All cards in the set are tournament legal. It will be available in booster packs, theme decks, and Fat Packs.
Starting with Time Spiral, there has been a change in how premium cards are distributed. Previously, premium cards replaced a card of the same rarity, so a premium rare would replace a standard rare, a premium uncommon would replace a standard uncommon, and a premium common would replace a standard common. In Time Spiral and in future sets, all rare, uncommon, and common premium cards will replace a standard common instead. It is now possible for there to be two rares in one pack: the standard rare card plus a premium rare (which replaces a standard common).
by Scott McGough and Timothy Sanders
Time Spiral Cycle, Book 2
Teferi Planeswalker sacrificed his powers to mend the splintering Multiverse, but it was too little and too late. An unnatural cold has taken root in Dominaria and is spreading. Now powerless, Teferi tries to find a way to finish what he started before the world is destroyed by the havoc he unintentionally wrought.
To learn more, go to the Planar Chaos book product page.