RTF is a global modification that replaces all towns in the game.

https://mightandmagic.fandom.com/ru/wiki/Вольные_Города

There is very little information about Listmur – literally 4 lines on the wiki.

Also, in Heroes 5, Kurak attacked the Duchy of Voron, which means he must have passed through Listmur... and if you think about it, the Grimheim opposition (Clan of the Steel Hammer and Clan of the Deep Flame) could have fled there after Wulfsten came to power (when the regicide says that Arcat chose him, it looks suspicious -_-)