Sliver Gravemother

The "legend rule" doesn't apply to Slivers you control. Each Sliver creature card in your graveyard has encore {X}, where X is its mana value. Encore {5} ({5}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)