Tidal Marsh Trap

(Nonexistent mana costs can't be paid. Tidal Marsh
is blue and black.)
You may pay {1}{b}{u} rather than pay this spell's
mana cost if three or more counters were put on
permanents this turn.
Each creature gets -X/-X until end of turn, where
X is equal to twice the number of counters on it.
Then put each land with one or more counters on
top of its owner's library in any order.