Remake of the classic Warlords 2, Warbarons. Turn based, online multiplayer strategy game. If you did not play Warlords, it is somehow similar to Heroes of Might and Magic or Age of Wonders. Gameplay differs as you can move any single unit around the map. This combines strategy and tactic parts into the main map and allows for correspondence multiplayer games. Like the old play by email (pbe), but smooth.
The game is browser based, so it can be played on pc or mobile. For mobile, I recommend some full-screen browser.

Start your game with tutorials. Pass them all. Read the whole wiki, especially 90% rule. Pass all challenges. The community is quite challenging. For quick start, You can try to arrange 3vs3 game and look what your allies do.

The assassin hero is quite interesting as he allows for solo city capture. But note that ambush is twice weaker than leadership. Barbarian would also be able to solo your expansions, due to the 90% rule.

Overall, have fun, and keep calm when your favourite hero would die with the whole army in some unbelievable battle.