Karrthus, Hive Tyrant

Slivers you control have flying and haste.
When Karrthus, Hive Tyrant enters the battlefield, gain control of all Slivers, then untap
all Slivers.
"When the Slivers arrived on Jund, after a fierce
battle, they assimilated the king of the dragons. The
hive on Alara soon unified all Slivers, regardless of
plane or origin."