Abandon all hope, ye who enter.

In a time before there was time, there was Leviathan. Leviathan saw the multiverse, and saw that there was sin. And so the Underworld was forged, the great god-pillar and his titan architects forging the plane from nothingness itself to be the final resting place for the wicked and the damned. For aeons, Leviathan's great magicks have plucked the wretched and the foul from across the multiverse to be punished for their deeds, and the raw energy of their despair has wrought demons, devils, and nightmares into being, a vicious cycle of pain begetting punishment.

However, cracks are beginning to seep into these ancient foundations. Across the fabric of the multiverse, something has ruptured, far beyond the lidless sight of the Heart of Sin. But in the blackened skies above Mount Purgation, a sliver of light beckons invitingly--a path of omens, the damned whisper. A hole in the sky; a candle in the blackness. A way out.

Circles of Bocacius is a draftable premier set using Play Boosters, containing 266 cards (20 mythic rares, 60 rares, 100 uncommons, 81 commons, 5and 5 basic lands).

Mechanics

The mechanics of Circles of Bocacius include:

The Underworld: Descending through the circles of the Underworld, the damned discover fresh and agonising punishments at every turn. When a card instructs you to journey into the Underworld, create the Underworld as an object in your command zone similar to dungeons or emblems, and put a damnation counter on it. Every time you place a damnation counter on the Underworld, choose one of its effects to trigger, so long as that effect's value is equal to or less than the number of counters on the Underworld. Some cards will care about when you journey into the Underworld, and others may upgrade if you've done so a certain number of times.

Penance: Those who feel their guilt the sharpest will wail the loudest. Penance is an alternate casting cost for spells which allows you to replace certain numbers with the greatest power or toughness among creatures you control. Rally behind a moral paragon and allow their example to show you salvation.

Descend: Returning from Lost Caverns of Ixalan, descend is a marker asking you to note when a permanent card enters your graveyard, whether that be from the battlefield, your hand, your library, or anywhere else. Make use of mill, combat, or sacrifice effects to get the most out of your descent into damnation.

Unearth: Returning from Shards of Alara and The Brothers War, unearth allows your permanents to be given a second chance--paying a card's unearth cost while it's in your graveyard will bring it back to the battlefield for one more turn, before exiling it after its final breath. Get one more attack in with your creatures, or one final burst of value from Auras or artifacts, as the damned grasp for one more chance at salvation.