Stop Sigil

Creatures can't attack or block, and their
activated abilities can't be activated. Whenever a
player casts a spell, put a time counter on Stop
Sigil. During your upkeep, sacrifice Stop Sigil
unless you pay {x}, where X is the amount of
time counters on Stop Sigil.
"Look, Dovin Baan! This Stop Sigil has 1, 2, 3, 4, 5,
6, 7, 8 glorious sides, and 1, 2, 3, 4, 5, 6, 7, 8
stunning angles! This Stop Sigil is an octagon!"