I like replacing Dovin, Hand of Control with Davriel, Rogue Shadowmage . Davriel can always help us win the game, whereas Dovin can just be sitting on the board doing nothing sometimes. I also agree with adding Kaya's Wrath and taking out Deafening Clarion . My concern is Kaya's Wrath coming down a turn later. If that turn matters and the three damage would be a board wipe most of the time, I'll switch back to Deafening Clarion .

I would add Tibalt, Rakish Instigator to the Sideboard at least. As long as the Explore package is in Standard it feels really good when he drops. Also, Esper control has a lot of incidental life gain and it may help there.

Bedevil is a really good card and it provides you with additional instant speed removal. I would consider it. You really don't need the creatures in your sideboard. Your planeswalkers have plenty of win conditions, and they just provide fodder for opposing removal.

Widespread Brutality works really well with Dreadhorde Invasion as a sweeper and can potentially gain you a LOT of life if done post combat. I found it mostly to work well against opposing aggressive decks as another sweeper option.

Normally I make suggestions as to what to remove for each card, but I haven't playtested the deck yet. Mardu is my favorite 3 color clan, and I really like this mix. I'll playtest a bit and come back for more. Good job!

Boroswins thanks for the suggestions and the upvote!

I like the idea of Tibalt, Rakish Instigator in the sideboard. I’m thinking it’s a 3 of and I take out the Lyra Dawnbringer s and the Rekindling Phoenix s and find something to take that fourth spot.

I do like Bedevil as well. It doesn’t feel great in those situation where you don’t have exactly BBR though. Maybe it’s a two of?

I’m not a huge fan of Widespread Brutality . It does work well with Dreadhorde Invasion , but without one on the battlefield it’s not that great. It deals one less damage than Deafening Clarion , but you do get a 2/2. I feel like four mana, I’d rather have the guaranteed board wipe in Kaya's Wrath .

I agree that Widespread Brutality is the worst of those three options without a 6/6 Zombie Army. I playtested now, and would probably just drop the Dreadhorde Invasion for 3x Bedevil . Your mana base has the flexibility for it. If you are worried, you could go for Angrath's Rampage instead, which also has a lot of value in your colors. How does this deck run against Mono Red? If it struggles, Aurelia, Exemplar of Justice has won me a lot of games by itself in that match. If no struggle, then nevermind.

As far as that 4th SB slot, +1 Vraska's Contempt is never a bad choice while Phoenixes and Planeswalkers are big in the format.