Open the Vaults: Play it after you have exiled all or most of your opponent's graveyards
As the games go longer, the windows for getting damage on your opponent will be smaller
What this means is you place all of the Vanguard cards facedown on a table and let each player select one or more, depending on how many players are involved
She is just so dangerous for her cost
Also, pulling a land out of your deck, or drawing that card off of this spell ensures your hand wont be hurting too much after it resolves
(By contrast, if you leave the game while controlling permanents owned by another player you gained control of, those control-changing effects end and the permanents return to their previous controllers.) (2021-09-24) If your commander is under the control of another player as you cast Visions of Dread using its flashback ability, that commander's mana value can be used to determine the value of X