For the vast majority of my test games, once I cast Purphoros one time, he'd stick around for the rest of the game
By the time the TCG became fully established, much of the first edition had already sold out, making these cards particularly rare and sought-after
Reprinted in Jumpstart: Historic Horizons and again in a Secret Lair, we otherwise haven't seen Bonescythe Sliver since Magic 2014
On the other hand, if you are targeting and controlling an opponents graveyard yourself, Havengul Runebinder is of use, which can remove creature cards from any graveyard for 2Bl to create a 2/2 Zombie token and put a +1/+1 token on each Zombie controlled
Main targets are always Mishra's, not mana sources, because under the Void the opponent will play just one spell a turn anyway
In other news, Valduk, Keeper of the Flame players found their favorite new card