The "legend rule" doesn't apply to Slivers you control.

Each Sliver creature card in your graveyard has encore , where X is its mana value.

Encore (, 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.)

All Sliver creatures get +1/+1 for each other Sliver on the battlefield.

: Create a 1/1 colorless Sliver creature token.

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Sliver spells you cast have cascade.