When inside a tower with a group and having Lord aggro the Tower or Keep Lord will, once attacked, keep attacking the group of players who attacked it. Even when moving to lower levels the Lord will resume attacking random members of the party, then disappear to reset and then instantly aggro on someone else in the group.
In the process the Lord ignores roofs, walls, stairs or pathing rules in general. The Lord will attack from or through walls without regard for LOS.
In addition, Animist shrooms seem to ignore LOS for casting inside towers on occasion as well, casting through non-existent gaps while players do not get LOS of them in return.