ToME: the Tales of Maj'Eyal

not necessarily a bug, but is there a reason these abilities are not passive? I am scratching my head trying to think of situations where you would not want these active. Given that, it'd be sweet to save a couple of icon slots
unless I'm missing something?

I think it's a technical issue. It's easier to write sustains than it is to create passive skills that act like sustains. Once I get any skill like that, I just set it to auto-cast, since it's a hassle otherwise.

These were made sustains to give them a little more flexibility. There may be situations where you don't want gloom (sneaking past something?) or stalk (you want to attack an underling before stalking an approaching boss?). Whether that is a good enough reason, I don't know. I don't think there is much of a technical difference that couldn't be worked out.