There are several places on the map, Where can you find Hell's Iron in Baldurs Gate? 3.
Go to the Extinct Village and go to the house, located in the north of the settlement. Enter a large structure, go through it and then turn right. Pass the main room and go to the annex to the east.
There is a large pit in the center of the extension, leading down. However, it is completely covered with a web and it will not be possible to get through it.. Use the Karlach skill, or any other skill/potion, capable of setting fire to surroundings. Go down to the basement. Once at the bottom, climb the stairs to the high ground and examine the nearby chest.
To open a wooden chest you need to hack it, passing an agility test. The dice need to be discarded 15 and more. Inside the chest you will find hellish iron.
To find an underground hideout, first visit the Waukeen Shelter location. Move to its western part, until you hit a dead end. Interact with the dilapidated door and enter the house to go to the next location. You must first pass a test in a conversation with a magician, to access the hatch.
Go down to the underground hideout, bypassing all the labyrinths, and move to the very north of the location. There are two rooms here, next to a dead end. The premises of interest are located at the coordinates 284 on X and 170 on Y. Along the way you will have to deal with all the enemies. Having reached the desired place, crack the grate, to get inside. The iron is in the right chest.
At Baldur's Gate 3 You can also find Hellish Iron in the goblin camp. You can get here through the story. If you saved the goblin Sazza earlier in the Emerald Grove, you will be able to get into the treasure area without any problems and carefully break into the cache. From the entrance to the location, move north to a dead end. If there are no thieves' tools, or the situation with Sazza ended violently, you can just kill the leader closest to the premises, to take the key from him.
Another piece of hellish iron can be obtained in Grimforge. Once here, From the teleport, go straight west. Near the rock you will find the stonemason Keith, who sells various things. Use all items immediately, increasing the chances of success during inspections, then talk to him. Pass three checks during the conversation, for which you will get a piece of iron from him.
REITVINSKAYA GUILD OF MASONS
During the story, the protagonist will have to go through Grimforge, and then get to the Moon Towers, and Shadow-Cursed Lands. When exploring this area, head northwest, to find the location marker "Masons' Guild". Move along the coast and cross the destroyed bridge.
Passing the bridge, you will find yourself in a forge. Turn left and look at the nearby workbench, there's hellish iron on it.
From the Masons' Guild, head north-west until, until you meet tiefling Raphael at the coordinates -182 on X and 102 on Y. Not far from it you will be able to find a descent into the dungeon Call Ball, where can you also find hellish iron in BG3. In the location itself you need to follow the left path to the huge hall. Hack the door to the north, then move to the storage room.
Perhaps, one of the most difficult ways to get hellish iron is to knock it out from Yurgir. While in the "Challenge Ball" location, go north, to coordinates -657 on X and -753 on Y. Here you will find a large hall, in which the boss Yurgir and his minions live. Before the battle, it is recommended to drink the maximum amount of enhancing and protecting potions, take a break to restore your health and prepare for battle. You can pick up hellish iron from the boss's body.
HOW TO USE HELL IRON
If for one reason or another Dammon is not in the Emerald Grove, go to the Last Light Tavern, by X coordinates: -27; Y: 159. In the location you will find a forge, and there - Damon himself. All that remains is to give him the resource.