Tom Bombadil (LTR #234)

As long as there are four or more lore counters among Sagas you control, Tom Bombadil has hexproof and indestructible.

Whenever the final chapter ability of a Saga you control resolves, reveal cards from the top of your library until you reveal a Saga card. Put that card onto the battlefield and the rest on the bottom of your library in a random order. This ability triggers only once each turn.