"Escape to Salvation" - "Magnificent Retreat" [Campaign 4, Mission 4]

I teleported, and then continued on to the Dungeon on the island beyond the bridge, at the bottom of the map.

Isn't it a portal there, rather than a Dungeon, which teleports you to the southeastern part of the map? I wasn't too lazy to replay it: the Demon Lord, Daleb, it seems, can be defeated even on automatic battle mode. I have 450 Sabotage Gremlins, 24 Storm Titans, 67 Battle Mages, 160 Magnetic Golems, 3 Phoenixes, 106 Air Elementals, and 20 Rakshasa Kshatriyas; against his 120 Hellhounds, 450 Cerberuses, 55 Cave Lords, 200 Imps, and 95 Fire Elementals. With Zehir's super skill, "Arcane Mastery," i.e., having all existing spells in the spellbook, the battle is won, but with considerable losses, and there are still battles ahead. I checked my saves and remembered that I simply cleared the southwestern part of the map and, without touching the demon, went through the portal. Destroying the demon is a secondary task, and then, at the very end, with the map fully revealed, I returned and defeated him; he was still standing near the destroyed bridge, where the garden with the leprechaun is. The computer won't always chase you around the map; it often gets stuck. So, go ahead and good luck!