I killed Sparky too!
It was Agatha all along!
You have 2 choices with this deck -
Drax - Not entirely sure, but this seems like the best option as it's there for a pattern of playing 2 4-drops on turn6, when we know lane threats. Hence, no Jessica, Rescue, or others that require a follow-up turn.
Domino - You can pick between Domino and Quicksilver here. You NEED one of the 2. Perk of Domino is +1 power, perk of QuickSilver is Agatha may play him into a mid lane Death's Domain, Luke's Bar, or Sanctum Sanctorum. Realistically, pick the one you have the bettter variant for. With 1-of QS or Domino in the deck, we have a ~77.7% chance to hit either Wave or Sif by turn3. If we cut both, we only gain ~4%, to 81.8%. If we try to run both, we drop to ~61.8%, which is too much of a loss to run both for added consistency in the late game...
So what is the lategame? First off, if we do not hit Wave or Sif on turn3, we are likely retreating if the opponent snaps (can stick it out until they snap or whatever if ya want). But let's say we hit 1...
If we hit Wave, Agatha plays her self on turn4, and we move to the lategame plan below (for turns 5 and 6).
If we hit Sif, you'll have to use your best judgment on what to play on turn4. Mary, Ghost Rider, Drax, and Jubilee can all technically be alright (depending on handstate - see more on this later).
Our deck has 2 5-drops: Sera and Taskmaster. These are our ideal turn 5 plays after Agatha. Taskmaster is a 14 power body, Sera opens up our turn 6 to be double 4-drop (which we have a high density of within the deck). If we discarded Agatha, you'll have to use your best judgment.
Now, this deck actually has a decent amount of skill expression, despite it being an Agatha deck, believe it or not. To make that statement even crazier, Jubilee becomes a main focus of skill.
We have to know what cards are left in our deck and play (or not play) Jubilee accordingly. With Agatha essentially thinning our deck to 11, the following card count is left in our deck, assuming no locations mess with it:
Turn 4 : 4 cards
Turn 5 : 3 cards
Turn 6 : 2 cards
On turn5, if we are missing both Sera and Taskmaster, we 100% play Jubilee (pick lane based on board...only 1 of Shang/Enchantress can be in deck, aim appropriately). If we have either 5-drop, simply play it. Realize if Jubilee pulls Taskmaster after Agatha played herself, Taskmaster will get Agatha's power, not Jubilee's.
On turn 6, with 2 cards left, we have a 50/50, and will very rarely (~2.2% ) have both Shang and Enchantress remaining in the deck. As such, aim Jubilee into the appropriate lane. If Ghost Rider is in deck and we discarded Agatha, make sure you play Jubilee into a lane with 3 slots. (edited)
Now, the reason we are playing Domino or Quicksilver is because we want to avoid all possible full low-rolls with Jubilee (and draws in general after the start of the game). We give up the 4% on hitting Wave/Sif to gain that all back in our lategame randomness. (edited)
Potential drawbacks/counterplay:
-Opponent getting a turn 4 Wave can cause problems.
-Unsure how playlines work out if we discard vs playing Wave.
-Really need to know what Jub pulls are in your deck when you have the option to play her. I did not touch on every possibility, as it depends on a lot more things such as locations, opponents board, hand state, etc.
-Respect Magik. If you think your opponent's list plays her, have a plan for turn 7. We have large cards, so we shouldn't be plain out, but think about it a little.