The Gravemother is simply there to provide reach for the deck, reanimating token copies of your slivers for one last beatdown
The reason why it was changed was most likely due to its depiction of an unholy ritual, as well as the two flags bearing images of skeletons
Plan B: Get my opponents to seven and finish them off with Bolass -4 ability
This makes taplands even more of a liability and the need to cash your lands in for action less important
The crowning touch for this theme is further down this list, but its duo Fire attacks, one dealing damage and another removing a troublesome Stadium card, this Charmander is a must for any Kanto-based Fire deck when its full evolution chain has been added
Dragons Rage Channeler works really well with previously mentioned Unholy Heat, since both care about Delirium, and they help each other out reaching that common purpose