There is no indications as such for Poison Tower in Edron being part of the Tibian lore. There might be some speculations which I will leave here, so maybe someone can get some extra ideas and investigate further.
Poison Tower was the idea of Knightmare which been confirmed by him in the interview with TibiaNews in the date: May 20041
"Some Ideas just don't work in the game at all and I am disapointed with the view, like the colossus infront of Kazordoon. Its realy hard to understand whats the concept of it, if you did not enter it and even then it needs a lot of imagination. Or the poison tower on Edron, it just did not look like I wanted it to look. Thats why I probabl never try my luck at a tibian sphinx as I planned to in the past ;o)"
Knightmare mentions that his inspirations comes from different sources: games, books, movies etc etc. Some of the elements are to add the "flavour" to the lore or created places. This suggests that Poison Tower was something which Knightmare seen, or read about in the past and decided would suit in region of Edron. As he mentions colossus along with Poison Tower- it seems that their purpose is to be seen and wonder about them- but not the enter the places (Knightmare confirmed that there is a key to colossus, but key is not with any of the players)2. Naturally, we can search on googles for Poison Tower and then we can discover following art pic which was inspired by Dungeons and Dragons- known Serpent Tower. The shape of the tower is different however there is similar concept of Snakes fuming the poison. Also DnD Serpent Tower was part of Empire of Scorching Sands so the Ankrahmun would be more expected for that tower.
https://www.deviantart.com/waronmars/art/Poison-Tower-637328806
Then the picture gave me a thought- what if it is for protection against Orc's? We cannot ignore Ulderec's Rock being west from Edron and there is no invasions or whatsover which we could expect to happen. The orc raids are only in the cave south of Edron. 3 Going deeper- the Tower is invaded by Wyerns, and those monsters by the lore are creation of Shaman Orc's.4
It can be also opposite- tower was maybe the center of creating Wyerns, full of toxins which were used on flying reptiles to create them. Orc's abandon the tower, however, it still produces toxins which can affect or attract those reptiles.
Additionally, There is a video from December 2021 where player Maxigash was exploring the places not accessible by players. Time on the video with the focus on Poison Tower 4:22- 4:54.
https://www.youtube.com/watch?v=kGQrdIUVvvs
On the video we can see that most of the things inside are left without any much of content (no books, no scripts on graves, no special items). There is no teleport to the Tower itself, but it is believed that it can be accessed somehow from the corridor (hero caves corridors) which is directly underneath.
1. https://web.archive.org/web/20111105153731/http://www.tibianews.net/component/content/article/83-interviews/682-interview-with-cipsoft-knightmare.html
3. https://tibia.fandom.com/wiki/Edron_Raids
4. https://tibia.fandom.com/wiki/Wyvern
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