To start, the initial reprint value is over $200 at time of writing this article which is already a huge jump in value estimation, especially for an in-universe precon
Its most effective after your opponents exhaust their removal on your initial threats
Sliver Gravemother Sliver Gravemother will benefit from cards such as Mirror Box and Helm of the Host as backup cards if it gets removed
From there, you can pair these flicker effects with cards like Peregrine Drake, Palinchron, or a basic land (in the case of Ghostly Flicker) for infinite mana, Overwhelmed Apprentice to mill your opponents out, or Venser, Shaper Savant to return all opposing permanents to their owners hands, just to name a few of the possibilities
Then, slowly, slowly, its hand raised, and an earth- and blood-caked finger gestured east