An ID window on the back
Once per Chain, when a Monster Card your opponent controls activates its effect (Quick Effect): You can either detach 2 materials from this card, or destroy 1 "Dark Contract" card you control, and if you do, attach that opponent's card to this card as material
But there are a handful of other high-price reprints, like Kozilek, the Great DistortionKozilek, the Great Distortion, All Is DustAll Is Dust, Eldrazi TempleEldrazi Temple, and Forsaken MonumentForsaken Monument
Other options related to auras are Siona, Captain of the Pyleas and Syr Armont, the Redeemer, but these are just reprints that fit the decks theme
At this point, my son and I have played around 15 games and are starting to get the hang of things, but our decks seem somewhat badly built