Seeing no traps, Rethan calls the glaive back to his hand and walks into the room, looking around some more.

Titus walks stoicly into the room, he looks at the dwarven images on the doors, trying to place the culture in what he knows about the city.

History 10

After a few moments, Titus motions the Bugbears to his side as they proceed to make a perimeter of the room, marching with the Bugbears a half step behind him up the eastern side of the room and down the west side of the room, Titus stands ready to use his shield if anything strikes at him or the Bugbears.

Morph, still using Detect Magic, scans the room from the entranceway, as his friends search ahead.

Perception check to look over the room from the entrance: 6

Morph, oddly enough, finds only the door recessed into the walls is magical. 

Meanwhile, Titus examined the old ruins, identifying the dwarven bas-relief as originating from the ancient Clan Melairkyn that predates the founding of Waterdeep.

Mal follows the group in. "Tarry not! We wouldn't want to keep this vault's occupants waiting unduly." Calls a voice emanating from a space of thin air.

"Any idea which way?" Rethan asks, looking at the various doors.

The twelve sets of doors, easily labeled:

The entrance into this room is between the sets of doors labeled 1 and 12.

Still invisible, Mal's footsteps tip-toe over to door 3, to get a better look around. He fears there might be other dangers lurking behind the crumbling pillars of dwarven stonework.

Nothing leaps out at Mal, but the doors appear to be ornamental and do not open.

Seeing the way is blocked, Mal carefully circulates the room, inspecting each of the doors alongside Titus's inspection.

Titus shares what he k owe about the Melairkyn clan. After a few minutes of them gawking at the doors he shrugs and approaches door number one. He motions the bugbears to his side and says “I suppose this one is as good as any other, yes?”

If nobody objects he will attempt to open the door.

Many of the doors appear to be decorative. Trying each of them in turn reveals two sets of doors that are actually functional. On the other side is a set of stairs that climbs 4 or 5  stories into the dark heights of the vault.

On the north wall opposite the stairs is an elaborate fresco depicting dwarves and goblins in battle. Titus and the two bugbears stand for a long time staring at the fresco. In fact, as the others turn to go up the stairs, Laniel realizes that they aren't listening to the idle chatter and the announcement that it is time to continue. He goes back and pulls gently on Titus' upper arm. "It's nice, Titus, but we've got work to do," Laniel says.

Titus violently shrugs off Laniel's grip and returns to stare at the fresco. "Titus?" Laniel says but the paladin does not respond. He walks around to look at the dragonborn in the eye and finds him glassy-eyed and staring at the fresco, his mouth agape. When Laniel blocks its view, he moves to regain a better one.

"Fellows and ladies, we seem to have a problem," Laniel says to the group at the base of the stairs.

DM shield:

Morph comes over to Lanial's side, observing Titus's current state.

Without looking at whatever has Titus enthralled, Morph utters an arcane word and makes a gesture with his hand, causing a fake wall to appear between Titus and what he is looking at.

Action: Cast Silent Image: Creating a fake wall up to 15ft by 15ft, to completely block line of sight to the northern wall and anything on it.

"Come on Titus, snap out of it friend!"

Everyone holds their breath for 10 seconds while they wait to see if the Charm spell wears off. But the three enraptured party members hardly even blink, staring now at a seemingly blank wall.

Esvele Rosznar forcibly sighs. "Leave them," she says. "We don't need their help."

Morph:

Even invisible, Mal's expression is evident in his voice. "You can't be serious. Never leave a drinking buddy behind!" Mal approaches Titus and examines him closely. "What is this? A charm? Paralysis?"

Titus is definitely not paralyzed. Trying to pull him away, he fights himself free, returning to stare blankly at the wall.

OOC: Titus is charmed, So I’m not able to take any actions right now, correct?

Correct.

With a frown, Morph lets the illusion drop, allowing the painting to be seen again.

Still not looking at the wall with the painting, Morph flicks through his Medics handbook.

Finding something that might help, Morph tries casting another spell.

Uttering another arcane word and placing his hand on Titus's shoulder, a dim glow spreads from Morph's hand, over Titus's upper torso, before absorbing into his body.

Action: Cast Resistance on Titus: Once before the spell ends (1 minute, concentration), the target can roll a d4 and add the number rolled to one saving throw of its choice.

(if no saving through is happening, this wont do anything, but maybe saving throws are happening in secret? :P)

Morph watches his friend, hoping he will snap out of whatever has him enthralled.

 (No saving throw will happen again for quite a while, I'm afraid.)