Tome of Strahd

What we know

Locked leather tome with steel padlock and Ravenloft crest; captivating melody from attic dresser until opened (Session 19 @ 01:09:06)
Found in Vallakovich Manor attic storage—Victor Vallakovich's workroom above master bedroom (Session 19 @ 01:09:06)
Party believes: matches Nine of Swords · The Torturer tarokka clue—house of corruption / dark room full of still ghosts (Session 6 @ 02:52:00; party assembly after Session 19)
Party believes: still ghosts = Stella Wachter visible on ethereal plane in Victor's mirror (Session 19 @ 01:03:29)
Mercurio identified as Tome of Strahd and attuned during long rest at St. Andral's Church (Session 22 @ 01:50:00)
Opening triggers mist visions—shared dream pulled whole party into Strahd's past (Session 22 @ 02:05:00)
First readable page: Strahd's record correcting misunderstood history of his reign (Session 22 @ 01:50:00)
Vision showed young Strahd von Zarovich (~12) before birth of Sergei von Zarovich (Session 22 @ 02:05:00)

Unconfirmed: full attunement powers and further vision triggers (Session 22 @ 01:50:00)