game of thrones (the show) (SPOILERS)

[Tempest]

the tower of joy is when eddard stark and his boiz roll up on arthur dayne and his boiz because rhaegar stole eddard's sister to be his surrogate wife or w/e and had her locked up in a tower. that nigga was dead as shit so eddard came up to save his sister and the only survivors of the battle at the base of the tower were eddard himself and howland reed, and it's a huge point of theorycrafting and contention because we only have eddard's recount of the situation so nobody knows what really happened

eddard's sister (lyanna) died in the tower but she made eddard promise her something before she died and it's never been revealed what the promise was but it's clearly important because it was mentioned.