There are some good things about Feline Ferocity
Arena has featured a few different types of cubes: Their typical Arena Cube, the Arena Powered Cube, the Chromatic Cube, and the Tinkerer's Cube. These are all phantom events restricted to cards on the client and change significantly with each iteration
Notable Manifest Cards Since manifest isnt as well supported as other mechanics, there arent many truly strong options, but Hauntwoods Shrieker is one of the better ones to build around
Some parts of the Service are billed on a subscription basis
Whatever path you prefer with your graveyard superstars, you should try and sprinkle in a few medium-cost options and self-discarding ones as well just to reduce the inherent variance of what is essentially an A+B combo, albeit a very nonspecific one
You cannot activate a Set Normal Spell on your opponents turn, like a Trap Card, but you can Set them if you want to bait your opponent or if perhaps you have too many cards in your hand