Magnificent
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I completed this map with a Hero from Inferno. I played as the purple player and grouped all other players into one team. I chose Grok, but made Iranna my primary hero.
Marbas had almost reached my castle, Iranna took 7 Imps and... not what you might think, she simply won the battle 
Then Iranna moved forward and fought on the surface. At level 24 she got BDP; she has Sorcery 35, artifacts for -20% init, -4 Defense, -1 speed. All together this allowed her to defeat large armies with just a few units. Later I bought Grok a Tome of Darkness; he attacked from another side, killing everyone with Arch Devils under vampirism. The map is large and even two heroes couldn't be everywhere in time. I trained Deidra (Darkness) and bought out the enemy Carly (Light+Chaos), and fought actively with them as well. In the end, Iranna and Grok returned to the dungeon and captured the last two towns there. Defeated everyone in 125 days.
Walkthrough
Opponents were random; High Elf, Dwarf, and Demon appeared. Iranna was in the tavern, so I decided to play as her. The start is without a sawmill or mine, and there are mana problems since I played via Chaos. But gradually I developed and moved forward, where I met yellow Marbas. I surrendered to him and learned the town portal at home. I trained Grok; he has Darkness, but in the guild there is blinding and unholy Marbas had almost reached my castle, Iranna took 7 Imps and... not what you might think, she simply won the battle Then Iranna moved forward and fought on the surface. At level 24 she got BDP; she has Sorcery 35, artifacts for -20% init, -4 Defense, -1 speed. All together this allowed her to defeat large armies with just a few units. Later I bought Grok a Tome of Darkness; he attacked from another side, killing everyone with Arch Devils under vampirism. The map is large and even two heroes couldn't be everywhere in time. I trained Deidra (Darkness) and bought out the enemy Carly (Light+Chaos), and fought actively with them as well. In the end, Iranna and Grok returned to the dungeon and captured the last two towns there. Defeated everyone in 125 days.Excellent Multiplayer map, beautiful design, and I really liked the gameplay too. If anyone finds it boring to play (read the comments), put all enemies into one team and it will be more interesting; this can be done in the editor in a minute.
Many thanks for the map!