Oh, and when it comes to defenders buying you time to build up to when you can establish dominance via combo or control, nothing is better than these guys because they give you a card to keep digging to find that needed mana, combo piece, or removal
In this deck with 20 instants and sorceries, there is admittedly a real risk of missing
Thoughtseize should work well against control or combo decks such as the Ad Nauseam deck or even Scapeshift decks, and Nature's Claim will wipe out troublesome artifacts or enchantments such as Expedition Map, Chalice of the Void (if it's not set to one) or Ensnaring Bridge
But if you do, then like all mayhem cards, its just going to be great value
Its been great going into depth about the Power 9, so I hope that you found it as enjoyable as I did
Nothing feels more chaotic in Magic than flipping cards off the top of your deck to see what might come next