"Flight to Salvation" - "Summoning the Dragon" [Campaign 4, Mission 3]

Guys, my problem is that I used one "Tear of Ashera" in the second mission. I gave it to Duncan, he ran to the lower city, which joined on its own, and he "built" it there... In this, the third mission, I opened 6 obelisks, but the map for "finding the tear" is not fully revealed yet!!! Although Wolfsten is standing with a decent army at the crossroads between the "upper" underground city of the dwarves and the exit from the upper portal, guarding against enemies... I don't have enough strength to attack this city; I tried 3 times and failed... Another hero (level 9) is guarding my city and the exit from the lower portal, and a weak, level 1 hero is bringing reinforcements from the stairs to the surface and exploring the underground... Although there's not much left to explore, as I said, there are only 6 obelisks. The mage Zephyr found, in principle, the "green meadow" where the dwarven dragons or whatever they are called should be, but I haven't even gone there yet. Can anyone give me some advice??? HELP!!! I went and found the red key, went to the dwarf (what's his name, Ralph or something), assessed the situation, and went to buy everything that was in the "flying city," defeated Ralph, and watched the cutscene... But I still didn't find the tear...