The Oracle of Theros
The Oracle of Theros is a character in the Friday Nights miniseries Hero's Path, which revolves around the crew's interactions with the Theros block. The character has no physical appearance, existing only as a disembodied voice that interrupts a podcast Kathleen is listening to and begins to instruct her in playing mono black. A running gag in the series involves Kathleen attempting to conceal her interactions with the Oracle (who it is implied only she can hear) from Graham by claiming she was talking to their cats.
The Oracle is voiced by guest star Marshall Sutcliffe, who co-hosts the Limited Resources podcast which Kathleen is listening to when he first appears.