Quicksilver: Can also be Domino, take your pick. I'm using Quicksilver because I like the chance of being able to play on the second location before it flips. Further thins your deck.
Jubilee: Very important to this deck, her biggest strength is her predictable targets in deck. On turn 6 there will be 2 cards left, on turn 7 there will only be 1. When playing this deck, it is important to keep track of what cards are still in your deck.
Sif and Wave: Tools to get Agatha out of the hand quickly. Running no other 3-drops guarantees Agatha will play either on turn 3. You end up taking back control on turn 4 (Sif) or turn 5 (Wave). Of neither are drawn by turn 3 there is a high chance the game is lost. Jubilee: Low power cards and generally not what you want to see. Accept that this is a possible outcome and play accordingly.
Ghost Rider: Brings back your discarded Agatha. For this to work consistently this deck runs no other 6-cost cards. If Agatha played Wave on turn 4, you can still play Sif+Ghost Rider on the final turn with the help of Sera/Magik. Jubilee: Make sure there is enough room at the location for Ghost Rider to bring back his target, this means you should play Jubilee at locations with 3 open slots.
Magik: Can be drawn by turn 5 very consistently. If not, you can pull her out with Jubilee. A turn 7 is not necessary in every game, use your judgement. Jubilee: Pulling Magik out of the deck on turn 6 WILL extend the game to turn 7. This is a 1-in-2 chance on turn 6, but you have a 1-in-3 chance of drawing Magik going in to the turn.
Sera: Sera on turn 5 opens up a lot of turn 6 options, allowing you to play a combination of two of any of your remaining cards, provided none are Taskmaster. This is likely to be your turn 5 play, followed by your control cards on turn 6.
Taskmaster: Agatha (played turn 4 using Wave) is the best target in the deck. Taskmaster will copy the current power of the card, taking into account and location and card effects that affect the power. The second-best target is Sera or the big 4-cost card, but this is a large step down. Jubilee: Taskmaster will copy the card played BEFORE Jubilee, due to how On Reveal effects resolve before the card enters the board.
Enchantress and Shang-Chi: Control cards played on the final turn to secure you a location, can play both on the final turn with the help of Sera.
Drax: A high-power 4-cost card that can be played on the final turn if the control cards are not necessary. Can either be played turn 5 to copy with Taskmaster on turn 6, or as one of the two cards you play on turn 6 using Sera's discount. Replaceable with any of the suggested 4-cost cards.