"Ahem, gentlemen, should we perhaps investigate that basin before standing in front of it? It´s warm enough as it is."
Selene stands back a bit hoping for Raadox or Daerryl to take care of any traps that might be triggered.

Daerryl moves to check the place for traps, pressure plates, hidden levers, dead falls, etc etc

investigation 7 advantage for favored terrain? 21 

Raadox will cast an eye over the basin using his previously cast Detect Magic and will have a check over for traps the like too.  If the spell has run out he will recast it as a Ritual, taking 10 minutes to do so.

Investigation (+5):  21
Investigation (+5):  11   (second roll in case of Advantage from help)

 Selene will assist, giving the help action to Daerryl and Raadox if possible.

Daerryl you see no traps or other surprises hidden in the room

Raadox, you see an aura of conjuration coming from the fountain. It seems that there is an enchantment here that upon being activated should cause the fountain to do something. It is very old magic and is only faintly still there. You think the trigger is probably spoken aloud based on the lack of keys or other traps in the room. 

Carvings on the western door show skeletal dragons. A Draconic inscription on the door reads, “Rebuke the dead, open the way.” Within 5 feet of the door, the air is noticeably cooler, and the door itself is cold to the touch.

 Noticing the coolness by the western door Selene asks Raadox "Any magic auras over here? Any of you gentlemen know how to rebuke the dead? Perhaps that is needed to open that door" Then she remembers that they have Meepo with them and turns to him. "My dear Meepo, can you please tell us which way we are going now" more than a little frustrated over the lack of guidance from their guide.

Meepo points down the corridor. 

Raadox, you see abjuration magic on the door

"Perhaps we should move on then and get back to all these magical traps at a later time gentlemen"

Raadox points out the magical emanations on the door and the basin, explaining that the door is imbued with protection magic and the basin has some sort of conjuration on it.   Let there be fire.  He scratches his head, looking at the basin a bit longer.  He then turns to the door.  Rebuke the dead, open the way.  Hmmm.

Raadox will swiftly examine the door, asking for Daerryl to help him quickly.  "Probably only openable by magic," he remarks to the little gnome as they work.  "But worth a look anyway".

Investigation (+5, adv): 22

Regardless of what they find, Raadox agrees with Selene.  "Yes," he says to her with a big smile.  "Let's let the little guide lead on.  We can come back here later, I'm sure.   By the way, those footprints you saw earlier, Daerryl?  They weren't goblins sized; they were bigger, weren't they?  Could they have been the adventurers we heard proceeded us into this ruins?"  I'm coming for you Ahnold.  Watch your back.

The door does seem to be locked via magic. You aren't sure what the trigger to opening it might be. 

Following the group and leaving space for them to look for traps, Kiori looks at the fountain and the carvings on the door. " I don't know about rebuking the dead, but if this says let there be fire we could try a torch later."

Quote from Blakey >>

Raadox points out the magical emanations on the door and the basin, explaining that the door is imbued with protection magic and the basin has some sort of conjuration on it.   Let there be fire.  He scratches his head, looking at the basin a bit longer.  He then turns to the door.  Rebuke the dead, open the way.  Hmmm.

Raadox will swiftly examine the door, asking for Daerryl to help him quickly.  "Probably only openable by magic," he remarks to the little gnome as they work.  "But worth a look anyway".

Investigation (+5, adv): 13

Regardless of what they find, Raadox agrees with Selene.  "Yes," he says to her with a big smile.  "Let's let the little guide lead on.  We can come back here later, I'm sure.   By the way, those footprints you saw earlier, Daerryl?  They weren't goblins sized; they were bigger, weren't they?  Could they have been the adventurers we heard proceeded us into this ruins?"  I'm coming for you Ahnold.  Watch your back.

 “Could be. I don’t like to assume and end up running into a Drow patrol, but it’s certainly worth following.”

 "Well, would the drow even leave footprints to find." Selene comments following Meepo and the others down the corridor "Why are you searching for these adventurers anyway Daerryl?"

“Oh, I’m something of a practiced hand at searching for people who’ve disappeared into the dark and dreary places of the world. These particular people have a wealthy aunt who must’ve heard of my talents, hired me to go looking.”

Interesting.  Seems like the little gnome might be looking to rescue Ahnold and his companions.  We may come to a disagreement in the near future then.  I won't let Ahnold out of this place alive.  He knows too much.

"What do you know about the adventurers you're seeking, Daerryl?"  Raadox smiles his disarming grin at the little gnome.

“I know they have rich family looking for them and what the tavern keep said back in town. Not sure there’s much else worth telling. Just another job.”

Raadox thinks back to the conversation in the inn.  "You said you were seeking a pair of brothers, Daerryl?  Do you know their names?   Let's see, the landlord mentioned a knight called ... Sir Braford I think.  And I think they may have had a ranger from the north with them.  The ranger stole something precious from me and I mean to reclaim it."

Raadox scratches his chin in a mannerism he learned from some of the rough humans he spent many years living and working with.   This could be tricky.  Is the amulet Ahnold stole from me worth crossing this group over?  Probably not.  But I am sure I can make it look like I'm the injured party.  Well, I am.  He did steal it from me.  Just because I cheated that fat merchant out of it in the first place doesn't make it any less mine.

“Whatever property disputes you have with others, that’s got nothing to do with my job. Take it up with the ranger. I just need to bring the brothers home. But for curiosity’s sake... what is it he stole from you?”

Raadox smiles his open smile at the gnome.  "He stole an amulet.  Nothing special or particularly valuable.  It was a family heirloom and of quite sentimental value to me.  But I'm still confused.  Who were the brothers?  Did they have names?  Are they in the adventuring group with Sir Braford and Ahnold the ranger?"

"A family heirloom is more valuable than a magical trinket, at least for my clan." Kiori adds "this person should return it to you once we found them. But first lets find this dragon."