Amareth, the Lustrous
Collection 30th Celebration September 16 The 30th Celebration arrives in September as a special anniversary expansion celebrating three decades of the Trading Card Game
Much like Oko, Thief of Crowns before it, Uro showed how tricky it is to deal with three-mana cards which can offer both battlefield presence and turn-on-turn resource advantage
Since its text states specifically a graveyard, it means any graveyard, yours or any of your opponents
Ah well, I think that's only a limitation that matters for a short period of time, as most people aren't going to care three months after release if your flashback deck had Grizzly Fate at the same time as your populate deck had token making engines
The deck that makes the most use of Solitude is probably 4c Elementals where it can be tutored up and then Ephemerated for some crazy value , but it is also vital for Azorius Control where it represents one of the few threats the deck can present