I don't know if anyone has mentioned this before and I went looking but didn't find anything. I haven't played arcanum since last summer but one thing has always bothered me. If vendigroth gets raised from the dead wouldn't they see Tulla as a threat after what happened with Arronax? I thought Tulla could then be placed under a siege by vendigroth and they would have to find a way to fight them off. I just find that this could be a nice little plot for a mod or sequel. (I don't see an official sequel anytime soon sadly) So what do you think?
Of course it would... However, it is questionable whether they would need to besiege Tulla because of the fact that Tulla wasn't meant to be a place that would threaten anyone. Tulla is meant to be some kind of monastery for mages. Pelojian, the founder of Tulla, seeing arrogance of the outside world had decided to gather those who would follow him and create a place for those that seek to live in peace and find their harmony inside their congregation, separating themselves from the outside world. If anyone was to start an offense, it would probably be Vendigroth, though, it is questionable whether they find Tulla or not, due to the fact that Tulla is meant to stay in secret. Even Perriman Smythe - the mage you can persuade to join your group, can not that easily reveal the position of Tulla on the map, being bound by an oath not to reveal that. Interesting would be though, how exactly would Vendigrothian government and their military forces proceed, revealing Tulla during the recon of the area of Vendigrothian wastes, seeing Tulla as non-offensive sector.
Talking about revived Vendigroth, aren't you curious who are the new Vendigrotians? If Arronax brought to life also its original inhabitatnts I doubt they would be able to adapt to new worls (don't forget that 2000 years passed) and therefore attack Tulla anytime soon. And if Vendigroth was newly inhabitated by techies from other cities, then they should have not feel any grudge against Tulla.
There were a few hints in the game that Vendigroth isolated itself from the rest of the world, so adaption wouldn't be much of a problem for them unless their resources changed over time.