The mask makes the tapper a dwarf, so Magda will produce a treasure token. With a single Tidewater Minion you have infinite treasure (mana), otherwise you need any two of the untappers above. The Mask also makes all creatures in your deck a Dragon, so you can effectively play any artifact or creature from your deck.
I imagine a deck using this combo will be UG, splashing Red for Magda. You would of course run 4 Emrakuls to win the game.