The Trolls fight on, but with only Troll 2 able to fight, aiming shots at Erix’s Panther:

Rend against Panther Attack: 15 Damage: 15 Slashing

Rend against Panther Attack: 20 Damage: 13 Slashing

Rend against Panther Attack: 16 Damage: 12 Slashing

You all are up, Chuztat and his Slaverer’s still fight you in the halls of the Troll Caves.

Oh and Troll 2 regained 15hp at the start of the round, and would have targeted any remaining attacks after the Panther died at the Elk.

Elero will cast Faerie Fire, trying to envelop all the trolls in it, but not any of the party or animals.  Any troll that fails a DEX 15 saving throw is outlined in bright green light for the duration of the spell, or Elero's concentration, and attacks against lit-up trolls are at advantage.

The Protector Cannon pulses out 10 temp HP of shielding to the party and animals.

LANDMOP will order the undead spirit to attack Troll 2

Attack: 23 Damage: 11

And try to hit it with a Chill Touch to stop its regeneration

Attack: 27 Damage: 28

The Elk and Snake attack Troll 2:

Elk: to hit 16 for 12 dmg

Snake bite: 16 for 6dmg
Constrict: DC14 strength save or take 13 dmg and be grappled

Erix tries to blow the Trolls backwards with a thunderwave:

DC16 con save or take 18 dmg and be pushed 10ft backwards half dmg on success.

Troll 2 Dex Save: 2

Troll 3 Dex Save: 8

Troll 4 Dex Save: 6

Chuztat Dex Save: 4

Troll 2 Con Save: 15

All the Trolls are lit up with advantage from Elero’s Faerie Fire, and LANDMOP blasts Troll 2. Erix’s animals hit, and then he steps in and blows the Troll up against the wall, killing it. Zoveldra and Mark both start laying into Troll 4

Troll 4 regains 15 hp and then

Chuztat Wis Check: 15

The four armed mutant yells at his two remaining luitenants, “Back to our caves, we can surround them there!” And they all Dash back into the caves beyond.

Zoveldra can Opportunity attack Troll 4

Undead Minion can Opportunity Attack Troll 3 (if that’s possible)

You all are up, the trolls have retreated into their part of the cave system.

You can chase the Trolls into their caves, keeping combat going. Or you could head south to an unknown part of the cave system. This southern path is disused and unbelievably smells worse than the Troll Caves proper.

(Could I get another con save for the undead minion's Aura? DC 15 or poisoned) 

Undead opportunity attack 

Attack: 26 Damage: 7

"Running blindly into the trolls' lair doesn't seem like too good of an idea, especially if they think it's a good idea that we chase them," Elero says, having translated the leader's yell from Giant.

"Maybe we regroup, and take the other path, and try to surprise them?  Maybe they have something else down here, and that's why the other area smells, so it might be best to proceed with caution whichever way we take."

Troll 3 CON Save: 19

Does everyone else want to explore this other tunnel?

(I'm good with that)

Erix agrees

Zo too.

You all head south down a wet and disused smelly tunnel, you get the feeling this part of the cave system sits apart from the Troll Caves. Are you going in stealthily or quickly checking out this part of the tunnels?

Stealth seems wise.

As your party Rogue, Mark stealths down the tunnel ahead. 

Mark Stealth check: 14