Aether-born Sliver

Slivers you control cannot be blocked.
Slivers you control have "If this creature would be sent to the graveyard by the effect of an instant or sorcery spell an opponent controls, exile that creature, then return it to the battlefield tapped at the beginning of the next end step".
"When our most powerful casters assaulted the hive, the slivers exploded into an ethereal mist. The moment we thought them dead they reformed and attacked from behind. They've grown clever indeed".