Built this on a whim after all my Hydra homebrews were just getting wrecked by simic flash over and over. Has been a blast to play in Gold so far and ive actually climbed a little bit as its matchup against scapeshift is really good. 

• Deck has 3 main win conditions, the most fun of which is a reliably fat, and always scaling Bioessence Hydra.
• Little Teferi + Mu can force a lot of early counters against simic/mono blue, or obviously if little teferi sticks, you can smugly drop a hydra and win via face smash.
  • Had a lot of success with Domri as well, but white offered way more power than red and I didn't want to play a lot of creatures.
• Cards that will ruin your day are elderspell, Gideon, and Adanto Vanguard (unless you can drop an early hydra).

The whole point is to run up to a big hydra on turn 4 or 5 but you certainly don't need to. You can definitely play a sort of control style with this list. If your opponent is control and has spot removal you will usually still win via Jace, or just recurring either hydra with Tamiyo until you inevitably get one to stick. They will also often ditch their removal after seeing all the planeswalkers and this will help too.

• One memorable game was:
  • Turn 6; 19/19 Hydra swinging at face, with Mu Yanling Ultimate, and a Big Teferi on board while holding a root snare.

I Run Fblthp > Growth Sprial because of Time Wipe, as I usually have to Time Wipe before I can play the Hydra against Aggro and want to maximize the card advantage while also still having a potential chump blocker early for my planeswalkers.

The original reason I ran 1 Vivien was to help deal with opposing planeswalkers during control matchups but her cost is pretty prohibitive and she's only had an impact in a very small number of games. This is a bit of a meme deck though, so I'm going to keep trying her out.

• The most memorable game I used Viv was to grab a Pelakka worm and recurred it with time wipe against RDW, made it worth it.
• Mu Yanling has overperformed, Kiora is always good as it can gap you the turn to time Wipe, early Hydra, early Teferi etc, lots of cards I run <4 of that you could replace Vivien with.
  • At some point I will probably remove her and maybe 1 copy of something else for 2x Deputy of detention to test.
  • I tried Samut, he's just way too weak on his own, and the deck is already struggling with room for everything.

Other cards I'm looking at are Healing Grace could be very a good bamboozle for your planeswalkers as well as being an easy, cheap recurring card advatage with Tamiyo against RDW, would probably not run more than 2 though.

• May also consider cleansing nova to deal with prison realms/search for azcantas or just overall flexibility of the artifacts/enchantments option.

Obviously you could just board out a lot of the fun cards and go full snare control, but why would you do that when you can win with a Hydra?