Bloodlust Siren

Flying
Whenever a creature with Haste enters the battlefield, if it has toughness 5 or greater, it gets
+4/-4 until end of turn. Otherwise, it gets +4/-X
until end of turn, where X is its toughness minus
1. It must attack each turn if able.
"The siren sings so sweetly that she lulls the mariners
to sleep; then she climbs upon the ships and kills the sleeping mariners." - Leonardo da Vinci