There was one other pony- well, not pony, Draconnequs- that knew Tirek. The Lord of Chaos himself, Discord. He reminiced on the time he helped him and his eventual regret, giving Twilight the final piece for Rainbow Power. The two definitely had history, to say the least. Flurry Heart asked if Discord could help her reform Tirek, to which he agreed- "It's what Fluttershy would want" he remarked. He offers to help release him from stone- he did help cast the original spell after all, and make sure he didn't absorb anyone's magic along the way. Now Flurry Heart had all she needed- at least as far as she knew- and once the sun rises the next day, Tirek would be released.
It's time to finish what Twilight started.