Deeproot Historian is a rare Creature — Merfolk Druid card from The Lost Caverns of Ixalan Commander (LCC), collector number 91. Current market price: $0.25, TCGplayer market prices via Scryfall.
Merfolk and Druid cards in your graveyard have retrace. (You may cast cards with retrace from your graveyard by discarding a land card in addition to paying their other costs.)