While the Worldsire doesn't have trample or any other form of evasion, it should be large enough that you can kill anything that crosses its path, and the land ability should be what you're using this for, with things like Valakut, the Molten Pinnacle or Field of the Dead
Put another way, for every two copies of Teferi, Who Slows the Sunset, theres three copies of Arlinn, the Packs Hope
There is one glaring downside in the fact that the card is only active during your turn, limiting blacks your impact on the game
Additional draw support Just in case you thought that was plenty of draw support as it was, this deck also runs several copies of Rapunzel Gifted with Healing to draw cards for each damage healed
Probably not good enough to last long if your opponent is playing any removal, but a neat effect if nothing else