Yes, such a game does exist.
Yes, such a game does exist.
Earlier, the studio behind Runescape released a spin-off called Armies of Gielinor on Fun Orb. Around 2010 most development efforts stopped, but the game still offered enjoyable gameplay and is now largely inactive. It featured a campaign with strong multiplayer features. Players controlled units via portals, using barbarian units to capture structures and earn mana for summoning more forces. Victory came from either destroying all enemy portals or reaching a target mana score. Looking for similar experiences is still an ongoing search.
The Battle for Wesnoth could be quite comparable. I put in a decent amount of effort.