As Magnus advances down the stairs toward the chamber Akiren uses primeval awareness, gasps softly, and mutters, "There is at least one fiend, one undead, and one dragon within a mile. One or more might be in that chamber, or beyond."
Riley casts Invisibility.
As Magnus reaches the bottom of the stairs he sees a chamber neatly carved from stone, 25' wide (10' to either side of stairs), 50' long and 20' high. There's another tunnel with more stairs down on the wall opposite of where they enter.
A small spiny devil flies near the ceiling in the middle if the room. A large skeletal reptile is coiled in front of the next stairway. Both stare at Magnus as he enters their sight.
Riley (adv +3) [rollv]2d20[/rollv