Yes, this is allowed by the rules.

You have to think these stones have pyramidal shapes. It's the only way.

thank you all above

Because of strange things like this, I like to play Descent using Imperial Assault line of sight rules. In those rules you cannot draw line of sight diagonally through any combination of walls/obstacles, which makes that particular tile more strategically interesting as a choke point.

In addition to line of sight, in Imperial Assault you also cannot move diagonally through two obstacles like that either. Unfortunately, while I would like to add the movement rule to my Descent games at well, it falls apart in practice. For example, the first quest of Mists of Bilehall, "Strange Awakening" requires that the heroes be able to move diagonally through two pieces of blocking terrain in order to finish the map. Too bad

Because of strange things like this, I like to play Descent using Imperial Assault line of sight rules. In those rules you cannot draw line of sight diagonally through any combination of walls/obstacles, which makes that particular tile more strategically interesting as a choke point.

In addition to line of sight, in Imperial Assault you also cannot move diagonally through two obstacles like that either. Unfortunately, while I would like to add the movement rule to my Descent games at well, it falls apart in practice. For example, the first quest of Mists of Bilehall, "Strange Awakening" requires that the heroes be able to move diagonally through two pieces of blocking terrain in order to finish the map. Too bad

I totally agree with you on the line of sight rules. My kids and I play both IA and D2E and we've tried the move rule and after a bit of "discussion" over the movement differences we opted to keep D2E movement and use IA's LOS. Exactly as Charmy points out, the LOS change makes many of the tiles a bit more interesting.