Auto-translated
1) Kobolds - PIT (1000 gold) - QUARRY (1500 gold and 5 wood)
2) Harpies - HARPY ROCKS (1500 gold and 5 stone) - SHRIEKING CLIFF (2000 gold, 5 stone, and 2 mercury) + BLOODIED SPIRE (1000 gold, 1 mercury, 1 crystal) (+4 growth)
3) Beholders - HALL OF GAZE (5 wood and 5 stone, 3000 gold) - ALL-SEEING EYE (5 ore, 3 crystal, 3 gems, 2000 gold)
4) Ettins - STALAGMITE VALLEY (15 stone, 4000 gold) - STONE FOREST (5 sulfur, 3 crystal, 3500 gold)
5) Illithids - ALTAR OF THOUGHT (5 gems, 10 wood, and 5000 gold) - SANCTUARY OF THE MIND (5 gems, 10 mercury, 5500 gold) ... + Mage Guild, level 5 (+2 growth)
6) Ifrits - GLOOM GORGE (10 mercury, 6000 gold) - ABYSS (5 sulfur, 5 crystal, 7000 gold)
7) Ogres - CAVERNS OF TERROR (20 stone, 15 crystal, 11000 gold) - DEVIL'S MAW (5 crystal, 10 sulfur, 12000 gold)
Description of the buildings' appearance:
Pits and Quarries.
Quarries (I think everyone knows what they are) and pits (like the ones used for laying underground pipes), and next to them is a Kobold camp... mostly tents, but there are also a few small huts (those who played Heroes 1 and remember the caves of Orcs, Goblins, etc.).
Rocks and Cliff.
Ordinary underground rocks, of which there are many underground, but only they have Harpy nests (they look like hollows in trees, but these are bigger and in the rocks)... when the upgrade is built, the upper part of the rock splits in two (i.e., two ends... for the witches and warriors), and the place where the rock splits becomes wider, and the harpies can gather there (like a clearing)... after the spire is built, there are three ends (the spire in the middle).
Hall and Eye.
Well... halls, that is, halls... something like the Town Hall of Armsmaster from Heroes 3, but there are no gates (i.e., open entrance), the roof is different (not a cone) and also open in some places.... in general, the building itself is more open (why would beholders live in houses?))... they also look a bit like Greek temples with columns.... when the Eye is built, a large eye appears above the hall (either on the roof or on a tower)... I don't know what kind of eye it is... nothing comes to mind (not like in Warcraft! But a living, enlarged eye of a beholder is also not needed)...
Valley and Forest.
Located behind the castle, in a remote part (behind the castle... like the Minotaur Stronghold in Heroes 3, only the valley is on the left (for us) and further on)... in general, there are many stalagmites, resembling dense forests, over which hangs a fog... when upgraded, stalactites appear that merge with the stalagmites and form vertical pillars, fog appears (maybe it will be a certain color or just ordinary)... and also, in this place, the dungeon will be lower (the ceiling is lower), so that... well, it will be better that way... trust my imagination!!!
Altar and Sanctuary.
A building similar to a sanctuary (temples, etc. or a Ziggurat), with a large staircase in the center... you climb it, and at the top there is an altar (where sacrifices, etc. take place)... that is, the staircase almost does not belong to the building itself) when you climb it, then the building begins... a room in the center of which is an altar... around the walls, rooms, etc. Of course, the center with the altar is open... the rest of the rooms are closed (roof and everything)... when the Sanctuary is built, some railings or pillars (lanterns) appear on the sides of the staircase with glowing blue spheres on top... maybe you can also make them all over the Sanctuary... or a tower (obelisk) in the center at the top of which there is a light... or light up the altar... I don't know what's better...
Gorge and Abyss.
It's simpler here... large cracks (gaps) in the ground from which hot steam rises, after the upgrade, rare flashes of reddish-purple flame appear.... (if you tilt the camera, you can look into the crack and see dark (purple) fire there.
Cave and Maw.
Caves similar to the hippopotamus lair from Heroes 3, only they are located in the dungeon... if the race were for Heroes 3, they would be instead of the Chaos Caverns or the Minotaur Labyrinth... when upgraded, the cave becomes like a maw, and a glow appears inside (maybe red).
Although the maw can also be given to the Ifrits, i.e., make a crack in the form of a maw... but I don't know... never mind.
P.S. Here, we have described the buildings of the units... we are waiting for comments, suggestions, etc. on the names, descriptions, costs...
P.P.S. Moderators of the section, rename the topic!!! The race is called "Dark Alliance", not Nigon