Demonsong, Scourge of Sarpadia

When Demongsong, Scourge of Sarpadia enters
the battlefield, search your library for a card, put
it in your hand and shuffle your library.
Equipped creature has "{b}, Pay 2 life: Equipped
creature gets +1/+1 until end of turn" and Double Strike. If equipped creature damages a player,
create a 1/1 black Imp token creature with Flying.
Equip {5} or tap 3 creatures with Necro you
control