Shadowheart And Gale Headline MTG's D&D Secret Lair Shadowheart is a good place to start, as that's clearly the set from this Secret Lair that Wizards of the Coast is the most excited about
Your main commander is Hearthhull, the Worldseed, a massive spacecraft that you power up by tapping your creatures
For as much as this set feels like a love letter to fans made by fans, there is one specific aspect that really rubs me the wrong way and adds a slight blemish to it
Plus, things like Eldrazi Temple, Urza's Mine, Urza's Power Plant, and Urza's Tower for even more top-end and explosivness
For six mana and requiring your deck to be full of garbage minions, whatever Muxus does needs to be flashy, powerful, proactive, and thematic
But yes, we are going back to the past, specifically pre-Modern era, so all cards discussed will hail from a time pre-O.G