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
These are equipment cards that come in but automatically create a 1/1 hero token they are equipped with
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
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