Erix looks around for Jas, not wanting her to flee (If she is already to far away/out of sight the attack will move to the closest gnolle) he tries to pull her back with another thorn whip

Attack: 24 Damage: Unable to parse dice roll. magical Piercing damage

The one Mark shot goes down with a bolt to the chest. The one fighting Centurion now has nowhere to run and is fiercely gnashing with its teeth.

Also I’m fine to use the ‘flanking’ optional rules if you all are. As long as you understand the monsters can benefit from those rules too. 

Jas is gone. Wormed away into the throng of Sharn.

Looking at the map. I don’t think you’re gonna be able to get into thorn whip range

If you're talking about what Elero did to gain advantage, I'm 100% ok with using that rule, and the monsters using it, too.  I didn't realize it was optional in 5e.

Kit still back there gagging eldritch blasts 

atk: 11 damage: 8 + 4 hex.

Kit's Eldritch blasts fly wide. The gnoll ducking and weaving fighting both Elero and Centurion.

Evelyn and Centurion are up. Erix can take a different action if he wants, as Thorn Whip isn't going to work in this instance.

Centurion slashes with his longsword while Evelyn fires an Eldritch Blast:

Longsword Attack: 18 Damage: 10

EB Attack: 17 Damage: 5

The gnoll, bleeding and alone. snarls one final cackle, "You've beaten us, but you've got no hope against Garra!" The gnoll shrieks as it disengages, and then takes it's chances with the luck of the Sharn flight. Jumping off the tower and on into the void. You see it flailing as it drops, and then it strikes a bridge about 40ft down, and the flailing stops as it drops into the ether.

With all the gnolls dead, you can now make any preparations you wanted to before heading to Terminus. Or anything else you wanted to do.

Mark will want to loot their body to see what they may have to help beat garra.

investigation: 14

Apart from the Shields, Hide Armour, Spears, and Longbows, the gnolls have very little on them. A total of 31sp and 18cp. As well as a few worthless trickets.

"Who needs healing?" Elero will ask to the group, ready to cast Cure Wounds on whoever needs it. "We should save our healing potions for the next fight, right?" He shrugs. "Or save my spell slots.  I'm good either way."

Mark will pocket the money and through the rest in the  center.

”I believe we should catch our breath and figure how to over this gang lord. These gnolls were probably not her best fighters and they still took a lot of energy to take care of. Do we really think we got what it takes to win out here with our lives?” 

"I'm fine for now, thank you, Elero." Kit says whilst nudging a knoll with his foot. His feral feline shift has worn off but the old cat still aint pretty.

He then turns to Mark "I think you're right. I was gonna say let's get on the next locomotive hot on Garra's trail. But, ... she seems to have a fair few tricks up her sleeve. We have a pretty good idea where she's going. The sergeant mightn't have much time though..." Kit hesitates, reevaluating if he really liked the sergeant that much after all and whether they should just call the whole thing off and hit the tavern for a bottle and a bet. 

The closest station, and the location of the Daask safe house where Vilroy is apparently located, is Terminus Station. So finding Vilroy and chasing down Garra would take you to the same location.

Make any preparations and plans you need to. I'll advance you forward to the station in around 12 hours. At that point i'll assume you head to Terminus on foot. If that is the case, you can take a Short Rest while you head over there. It'll take about an hour to get there from your current position.

"It does seem intimidating," Elero replies, "and I'm not sure about the sergeant now, either, but it feels like we've got to keep going if we want to solve this mystery.  I say let's heal up as best we can, and keep moving."

You approach Terminus from the skycoach crash, a grouping of towers with a skycoach platform at the top and a train station down the bottom. At this point you are approaching from the tower next door that comes out somewhere in the middle, in a section of Terminus with apartments. So you'll have the option to do one of three things:

1. Go up the tower stairs to the skycoach platform.

2. Explore the apartments on the level you are on.

3. Skip the apartments and head straight down the stairs to the train station.

Bit hard to describe properly as it's quite a complicated layout. Heres the view you have form the side:

"If I recall correctly, the train station was where Garra was making their escape, wasn't it?" Elero turns to the party. "Should we head straight there, or do something else?"

“We are walking into a trap, we should probably stop her way out before we go there or at least get the drop on the situation somehow by going through the apartments

"Also, if the serg is being hold here, I think the apartments make the most sense, no?" Erix points out