The place where you should be teleported to in order to solve the puzzle should also contain all the elementals; their groups are located in the same small area of the plain. The quest itself is purely for obtaining the Astral Gate, and the Necropolis is just a possible additional activity in the Dungeon, hinting at who helped the orcs open this tunnel.
I still don't understand under what conditions I should have been teleported. I gave myself a bunch of elementals using the console and left 500 Vanquishers for the exchange – it didn't work. I removed the Vanquishers, and it worked. I explored the entire map; maybe I'll play it again someday, for the quest with the fairies. I really liked the map; it's quite challenging, especially the last orc, if he doesn't run away, of course. Even my powerful Gigant couldn't break through him in the center perk under the dwarf set – I either had to change the light to get a general cleanse, but then I would lose the center perk, or just throw meat at him – and I was too lazy to do either, so after about 10+ attempts, I finally defeated the orc. When 15 Kirins under weakening kill 5 Daughters of the Sky, and they, in turn, kill 10 Kirins – I was just speechless.))
Tomorrow or the day after, I'll start playing the scenario that Astral called "very kind and positive" 
But overall, I really liked the general storyline for the Nagas. But it was while playing this scenario that I realized their full power. They are definitely ultra-imba. Ethereal, ranged ghosts that can even, when they are level 1, cast Crystal Prison – which, when used correctly, bugs out the neutrals – that's just amazing. As are the priestesses with Storm Strike. The upgraded Kappa and Mermaid can regenerate very strongly, and the Frenzied Kenshi can generally cause some kind of genocide of the enemy with the ability to overflow attack. With the center perk, the Kenshi produced simply amazing damage numbers. AND EVEN SO, I couldn't kill a regular orc under the King of the Dwarves set after the first 10 attempts.