Dark-Dweller Oracle
Creature — Goblin Shaman
, Sacrifice a creature: Exile the top card of your library. You may play that card this turn. (You still pay its costs. You can play a land this way only if you have an available land play remaining.)
Eyes are unnecessary for seeing the future.
Deruchenko Alexander
Core Set 2019 Promos (PM19)
• #134sRulings
You can sacrifice Dark-Dweller Oracle to pay the cost for its own ability.
(wotc • 2018-07-13)
Dark-Dweller Oracle doesn't change when you can cast the exiled card. For example, if you exile a sorcery card, you can cast it only during your main phase when the stack is empty. If you exile a land card, you can play it only during your main phase and only if you have an available land play remaining.
(wotc • 2018-07-13)
Casting an exiled card causes it to leave exile. You can't cast it multiple times.
(wotc • 2018-07-13)
If you don't cast the exiled card, it remains in exile.
(wotc • 2018-07-13)
Rulings
You can sacrifice Dark-Dweller Oracle to pay the cost for its own ability.
(wotc • 2018-07-13)
Dark-Dweller Oracle doesn't change when you can cast the exiled card. For example, if you exile a sorcery card, you can cast it only during your main phase when the stack is empty. If you exile a land card, you can play it only during your main phase and only if you have an available land play remaining.
(wotc • 2018-07-13)
Casting an exiled card causes it to leave exile. You can't cast it multiple times.
(wotc • 2018-07-13)
If you don't cast the exiled card, it remains in exile.
(wotc • 2018-07-13)