HBO has released a preview for the upcoming episode of Game of Thrones season 6 (Oathbreaker) which teases the tower of joy flashback. Check out the video below.
** Spoilers and speculation below **
In case you don’t know about Tower of Joy, it is a location in northern part of Dorne where Lyanna Stark was kept by Rhaegar Targaryen. At the end of Robert’s Rebellion, Ned Stark led the raid on the tower along with his companions and defeated the guarding Kingsguards. After entering the tower, Ned found his sister dying and she claimed a promise from him before she died.
Fans believe that the promise was an infant Jon Snow and he is actually the son of the Rhaegar and Lyanna (R+L=J). Ned’s promise was to never reveal Jon’s identity as Robert would have probably killed Jon if he came to know about his true parentage and therefore raised him as his bastard son. With Jon coming back to life in the last episode, it will be interesting to see if there is any truth to the most popular Game of Thrones fan theory.
There is also an alternate version of theory which claims Lyanna had twins and we met the other twin in last episode. Read about it here.