[Update #2]: MTG Arena's Alchemy: Murders at Karlov Manor mini-set is launching on March 5th, and it brings with it a potential teaser for 4-player games!
[Update]: MTG Arena has buffed a whole bunch of Domain and Powerstone focused cards.
If you're tired of Standard and looking to branch out into other formats on MTG Arena, this would be a pretty good time to do so. Not only has Wizards of the Coast just recently unleashed the Khans of Tarkir set onto Arena for Historic and Explorer players to enjoy, but they've also launched a brand new format focused around using as many broken and banned cards as possible - Timeless. Perfect to fill the gap until the next major set comes out in February!
First things first, the Khans of Tarkir set has been re-released in its entirety, so there are thankfully no missing cards like in some of the previous remasters. This does also mean that half of the fetchlands are now present on Arena, though given their extreme power level they're currently only playable in Historic Brawl and the freshly launched Timeless. So if you're planning to play either of the two formats, make sure to grab some copies as you'll almost certainly need them.
As for the rest of the cards added with Khans of Tarkir, those you can check out over at the official card gallery. Just don't be too surprised if you see a bunch of understatted vanilla creatures. Khans comes from a completely different era of Magic design - one where creatures were generally quite weak, outside of a few outliers.
Timeless, on the other hand, is a 60-card, ridiculously high powered format encompassing every single card ever released onto Arena, with no bans whatsoever. That said, three cards have been restricted and so you can only run one copy of them. The deadly trio is, unsurprisingly, Channel, Demonic Tutor and Tibalt's Trickery.
If possible, the cards in Timeless will use their original printing and will ignore any Alchemy-focused balance changes. As such, cards like Teferi, Time Raveler and Minsc & Boo, Timeless Heroes will once again be absolute powerhouses!
It's also important to note that the introduction of Timeless doesn't mean that Historic is going away or becoming less of a focus. The plan, according to Wizards of the Coast, is for Historic to be a finely tuned and curated format, while Timeless will be the Wild West where anything goes and where only the most obscenely overpowered cards will ever be touched. Or in other words, they're two very different formats for two very different audiences.
Whatever the future might bring next for MTG Arena, I'll make sure to let you know. Until then, have fun drafting Khans of Tarkir or simply turning everything the opponent owns into an elk, courtesy of the Oko, Thief of Crowns pictured above!