Restrainment Circle

Every player can have a maximum of four
creatures on the battlefield, except during
their turn. All players except the one whose turn
it is must sacrifice down to four creatures when
Restrainment Circle is played. This is only in
effect until Restrainment Circle leaves the battlefield.
"Your strength in numbers is gone, revealing
what you truly are: a miserable, pitiful, wretched
mess with no more power than a fly."