You can, at instant speed, do three things, but the Mana Leak won't counter anything, so what this does instead is bounce up to three things which can set back folks deeply, bounce two and replace itself, draw three cards when the bounce isn't needed, or bounce once and draw twice
This creature card's power and toughness are each equal to the number of nonland permanents a player controls
Mangara, the Diplomat: Sit Back and Control Mangara, the Diplomat gives you 2 ways to draw, once when an opponent attacks you with 2 or more Creatures, and when an opponent casts their 2nd spell each turn
Its very unlikely that youll be putting Swiftfoot Boots into the ninety-nine of these decks (unless you really want to win with Luxior)
Basically, "I wish I had my Tormod's Crypt." and then voila - Wish granted
Hopefully weve helped you to cut through the jargon and potential confusion with this guide