Mulliganing means you simply shuffle your hand back into your deck and draw seven more cards, and if its a hand you can keep, put one card on the bottom of your library
Kraven the Hunter was dead at this time, so he was replaced by Hobgoblin
If you dont want your opponents creatures, yours still receive some insurance against effects like Path to Exile and Deadly Rollick, which can be extremely helpful if a creature like Avacyn, Angel of Hope is holding the rest of your board together
Twilight Prophet Twilight Prophet looks to Dark Confidant and attempts to scale the card in a way that makes it meaningful in Commander, and it largely succeeds
Budget MTG Decks also has a great series of videos highlighting the basics, but youll want to pay special attention to the tenth (and final) video in the series , explaining one of Magics more complicated components The Stack
That's when it hit me