Dread Presence triggers whenever a Swamp enters the battlefield under your control, while the Arena triggers at the beginning of your upkeep
Here are my first seven two-color lists for you to check out: 1 I have not played Start // Finish, Campaign of Vengeance, Drana's Emissary, Executioner's Swing, Maw of the Obzedat, Purge the Profane, or Unraveling Mummy
You'll make six copies of Cloud, which then go and search for six more Equipment (before being removed due to the legend rule), and repeat the process every single turn
But even better is the fact that your opponents have to attack each other and their creatures will mostly be unblockable too, though the first two players to your left can deploy defenses somewhat
The fact that Brainstorm is a Legacy staple, and arguably even too good for that format, helps demonstrate how ridiculous Ancestral Recall is