Dabbert pulls the rope ladder experimentally a time or two, then decides it must be reasonably sturdy if the Baron has been using it to go up and down.  He climbs up, stepping back into the desolation of the city, and then draws his halberd and animates the shield that has previously been on his back.  The shield springs to life on its own, floating around his body, staying clear of the halberd in case he needs to move.  

The warrior steps to the forefront of the group and starts moving along walls and in shadows, keeping his feet light, moving with as much stealth as possible.  He shifts his body with expert skill to keep his armor and weaponry from making noise.  He's eyes up.  Watching for anything moving as he goes...

Akkron follows a few steps behind the cleric and the warrior.

"I should probably mention something before we get too far," he tells Lorlin. "Strange though it may sound... the standard healing spells which do nothing for the majority of undead actually work on me just fine... I found that out when a paladin who was under the mistaken impression that positive energy abilities would harm the undead tried to end me with a Cure Wounds spell, after which I did some of my own experimentation to find out if that was a fluke and determined that it was not. In case you were worried about the paladin... I didn't end him, though I will admit I probably bruised his ego pretty badly when I left him in a Forcecage after his plan backfired."

Perception checks all around, por favor! 
except for Dabbert. 

Perception: 12

Expending one use of Knowledge from a Past Life to add 1d6 to the result of that Perception check...

4

Perception for lorlin( advantage from sentinel shield) 

[Roll]1d20ad+12[/roll]  or passive 17

19 +12

Slip’s Perception 18

You all see the Baron Evernote’s raven familiar fly above and drop a small bag in front of you - A sturdy and expandable coin purse full of various roots and seeds. A closer inspection will tell you they are edible but not very tasty. 

"I think I'll leave this to those of us who actually need nourishment," the lich says with a chuckle, picking up the bag to inspect briefly before handing it off to whichever one of his fleshy companions is closest. "It was certainly thoughtful of the Baron to provide us with food, though. Perhaps we should bring something back to repay him for his hospitality... if we find anything worthwhile, of course."

As you make your way towards the ruins in the distance a white stone sword shoots out of the ground in a dangerous arc. It sails past Lorlin’s experienced reflexes as two stone monsters emerge from the sand.

20 feet in the distance two others shake off dust and begin to charge. 
 
 

(White and Grey on top of you. Vine and Gold 30ft away. Roll for initiative!)

Dabbert's Initiative!

21

Akkron's Initiative:

15

(Can I make an Arcana check to figure out what these things are/what their likely strengths and weaknesses are?)

Sure! Arcana or Nature to identify these freaks. 

Arcana: 35

Slips Init 18

Initiation Order: Dabbert, Lorlin, Akkron, White, Grey, Vine, Gold, Slip. 

Akkron: The ways these creatures appeared from hiding in rock informes you these are Galeb Duhr. But you known Galeb Duhr are only found on the material plane and never look like this. These were carved to look this way (either by someone else or themselves).

"Careful, I think these are Galeb Dhur!" Akkron tells the others, preparing to hit the stone guardians with a spell. "If they are what I think they are, then they could be bringing company soon... just keep hitting these ones and don't let up! Anything they summon only exists as long as they concentrate on it! Also, they're smarter than they look!"

 (Sorry for slow post-  Lorlin Init 21 in log (advantage from shield)