George R.R. Martin, the creator of Game of Thrones, said on his official blog today that work is proceeding “nicely” on three GoT-based series at HBO. But Martin cautioned against believing rumors about the shows.

“Oh, and speaking of television, don’t believe everything you read. Internet reports are notoriously unreliable. We have had five different GAME OF THRONES successor shows in development (I mislike the term “spinoffs”) at HBO, and three of them are still moving forward nicely.”

He added: “The one I am not supposed to call THE LONG NIGHT will be shooting later this year, and two other shows remain in the script stage, but are edging closer. What are they about? I cannot say. But maybe some of you should pick up a copy of FIRE & BLOOD and come up with your own theories.”

Bob Greenblatt, the recently appointed chairman of WarnerMedia Entertainment and Direct-to-Consumer, who oversees HBO, earlier confirmed to Deadline that conversations have been underway about continuing the Game of Thrones universe. “But we have to be really thoughtful about not killing the golden goose and not putting on shows that aren’t up to that quality level, and how many is too many. We’re having all those conversations. I don’t know yet what will come of all this material, but I think they’ve been smartly developing things that were really good ideas in this universe, and George Martin is involved. There’s a prequel in production, but just a pilot so that we can see if it has all the goods and is it worthy of going forward. We’re just trying to be really thoughtful about how to expand this universe if it makes sense, and not, like I said, kill the golden goose.”

Fire & Blood was a New York Times bestseller that takes place 300 years before the events of the current Game of Thrones. In it, House Targaryen—the only family of dragonlords to survive the Doom of Valyria—take up residence on Dragonstone.

Fire & Blood begins their tale with the legendary Aegon the Conqueror, creator of the Iron Throne, and goes on to recount the generations of Targaryens who fought to hold that iconic seat, all the way up to the civil war that nearly tore their dynasty apart.

Among the book’s subjects, related by a master of the Citadel:

What really happened during the Dance of the Dragons? Why was it so deadly to visit Valyria after the Doom? What were Maegor the Cruel’s worst crimes? What was it like in Westeros when dragons ruled the skies? The book is the first volume of the two-part history of the Targaryens.

Martin also took time to give a shout-out to Avengers: Endgame, calling it “amazing. Kudos to the writers and director. I cannot believe they got all those characters into one film, and still managed to do them all justice. The final battle was epic, exciting, thrilling, full of twists and turns… and strangely beautiful. But the character scenes earlier in the film really made it for me.” He noted that Stan Lee “would have been proud,” and also gave shout-outs to co-creators Steve Ditko and Jack Kirby.