Fruitcake Elemental is as indestructible as its namesake, and having it in play actively hurts you
The concept is simple
Rounding things out, I want you to pick up a copy of Commanders Plate
Unless youre willing to play the terrible Phyrexian Tribute, or the mediocre-and-expensive Gate to Phyrexia, youre out of luck if you want to deal with artifacts in Mono-Black
Knotvine Mystic For decks that want splashy spells or expensive creatures, Knotvine Mystic is a strong mana dork that taps for all three Naya colors
Surprisingly, Invasion of Shandalardoesn't have any restrictions on the permanents you can Regrowth, which means in a graveyard deck, you can set up some absurd value loops by using the battle to return two permanents and another copy of itself to your hand and then doing that again the next turn, but this is pretty slow