These are equipment cards that come in but automatically create a 1/1 hero token they are equipped with
The floor on Mystic Confluence is drawing three cardsessentially a Jace's Ingenuitywhile the ceiling is a three-for-one when you can Mana Leak an important spell, bounce one of your opponent's creatures (or even your own Snapcaster Mage), and draw a card along the way for good measure
The way this works is if a player has unspent mana in their mana pool, they lose that much life when phases change and that mana disappears
The starting player skips their first-turn draw (Comprehensive Rule 103.8a), so on the play you have seen 7 + (turn 1) cards by a given turn, while on the draw you have seen 7 + turn one more, because you draw every turn
Commander decks featuring this partner usually include equipment like Colossus Hammer, Blackblade Reforged, and Argentum Armor