The Mirrored Sliver

Sliver creatures you control have myriad.
(Whenever a Sliver creature you control attacks, for
each opponent other than defending player, you may
create a token that's a copy of that creature that's
tapped and attacking that player or a planeswalker
they control. Exile the tokens at end of combat.)
Every Sliver is reflected manyfold within the crystalline caverns it calls home.