You then get Lefou back to your hand and can exert Madam Mim to play Lefou again, ready her again, challenge again, etc
Its strong, its a shell for the nine, and it gives you a strong combat win condition in Dimir, which it has been crying out for
Several cards on this list helped matters get to that point so quickly, but seven cards will almost always equal trouble
Use effects that cost life to fuel Rowan's cost reduction then cast powerful black and red spells that would normally be far too expensive
Thats a serious blow to its ranking if they do
The constant threat of extra card draw for you makes Rhystic Study a staple in blue-based Commander decks, and you'll be surprised the lengths some players will go to to prevent their opponents drawing extra cards