While we don't have those to reveal, an example given in Turbo Gear's store description is equipping The Reaver Cleaver, reimagined here as Knuckles's Gloves, to Knuckles himself
From one returning mechanic to another, this is the double Hideaway card teased in Gavin Verheys Commander Hints video
The Crystal Cycle Taking a cue from the cycle of Medallions, we have the cycle of Crystals, which at least casual EDH decks will be interested in playing
This is a deck all about putting artefacts into the bin, pulling them back out for free, or doing something tricksy with them when they're in there
Thanks to the wording on Mayhem, you can wait until the end of the turn to cast Swarm, unlike Madness, where youre forced to do so right away