There are exceptions to this depending on the meta at the time and the format youre talking about, but four mana really seems to be the sweet spot
Suspicious Stowaway / Seafaring Werewolf The lone blue creature among werewolves, Suspicious Stowaway by itself is just a nice evasive value creature
For example, Ragavan, Nimble Pilferer already has the ability to Dash and being able to return it to the hand is important in certain matchups, and Orcish Bowmasters doesn't have a good body and part of its appeal is to cast it on your opponent's turn to kill a creature or punish a draw
This deck has issues that can be attacked, all explained via Niv-Mizzet, Parun
Power / Toughness: 5 / 1 / 4 Card Text: More Than Meets the Eye
only preventing combat damage from your opponents creatures means you can make many favorable blocks, and so few people play Fogs in Commander anyway that you dont need to worry about your opponents playing around it