I haven't fully fleshed out this deck, yet, but it's performed pretty well in the "Competitive Metagame Challenge" so far and decently on ladder. Granted, this deck has fallen flat against several off-meta decks, but done well against the standard teir 1 lists.

It's basically an "upgraded" version of Esper Midrange from last season. The basic package hasn't changed.

The appearant strategy is either to swarm the board with heros and 1/1 tokens in either the early game before the opponent can respond or late-game after the opponent's removal has dried up. Admittedly, I never thought this was a very good gameplan as hero dies to too many things in the format. However, the aim of this deck diverges from last season's strategy with the inclusion of elementals from Core 2020.

We're actually just trying to create sacrifice fodder for our elementals to make a 3/3 or destroy and opposing creature. Cavalier of Dawn in particular synergizes with Oath of Kaya as it can sacrifice it when it comes in and bring it back when it dies.

Hostage Taker and Thief of Sanity, both staples of the esper midrange archetype, have significant setbacks that always made me weary of their inclusion. Like Hero, Thief of Sanity dies to nearly everything and can become irrelevant in the late game, especially against Nicol Bolas, the Ravager // Nicol Bolas, the Arisen and God-Eternal Kefnet. Hostage Taker's body sometimes overwhelms against green and red decks--if it dies to a Lightning Strike before we have the mana to cast the creature we exile, they get it back. But now we can either use them as sacrifice fodder or as part of a plan to control three or more permenants of our opponent's to trigger Agent of Treachery. While I haven't had a game yet where this went off, Agent of Treachery has still performed exceedingly well as it can target anything (even lands) and the effect happens immediately.

I've always felt Esper Midrange lacked card draw and this is just about the best in the format. It even sneaks past Narset, Parter of Veils' effect as it doesn't say "draw".

Sideboarding

The sideboard plan is usually pretty simple.

• RDW: We can trim Thought Erasure to just one copy and add Despark in game two, anticipating a Chandra planeswalker or Experimental Frenzy, if not Rekindling Pheonix. Elite Guardmage can replace one big Teferi and one little.
• Command the Dreadhorde: That's what Garfdiffer's Cage is for, and we might need to run more than one if the meta leans too much in this direction. Also Dovin's Veto. Against the Wildgrowth Walker varient, I'll cut Teferi, Time Raveler entirely and might consider Cavelier of Night since it can gain them life if they steal it. Bring in Despark, for sure. 

Most other decks I've run against, either the deck is already in a good shape, pre-board, or there are obvious picks/cuts.