Even miles away, if you put your ear to the sewer vents, you can hear the screams and the tempestuous laughter.

Rix Maadi, Dungeon Palace

{T}: Add {C}.
{1}{B}{R}, {T}: Each player discards a card. Activate only as a sorcery.

The List

Commander 2019

{T}: Add {C}.
{1}{B}{R}, {T}: Each player discards a card. Activate this ability only any time you could cast a sorcery.

Dissension

{T}: Add {1} to your mana pool.
{1}{B}{R}, {T}: Each player discards a card. Play this ability only any time you could play a sorcery.

When the second ability resolves, first the active player chooses a card to discard, then the nonactive player chooses, then all chosen cards are discarded at the same time. No one sees what the other players are discarding before deciding which cards to discard.