Erix calls forth his hawk spirit again (Mark You can have 1 attack with advantage each round) and also summons a land beast.

Both the land beast and Chumulk are ordered to attack Dolgrim 2 first and protect the cannon.

Chumulk
Ferocity: 3
Bite attack: 25(Crit) for 10dmg

Land beast:
Bite attack: 26(crit) for 16dmg

Whew.  In all of that flurry, only one attack landed, against the Cannon.  Elero recovers his wits and lashes out with his daggers.  If Dolgrim 2 is still up (I suspect it's not), he'll try to finish it off, otherwise he'll attack Dolgrim 1.

Magic dagger attack: 15 to hit and 7 damage

Normal dagger attack: 9 to hit and 2 damage

The dented Protector Cannon will pulse out 9 temp HP to anyone who needs them.

Mark will move backward and attack the second Dolgrim to kill it immediately. 

Attack w/ adv: 21

Damage w/ sneak attack: 10 + 8 = 18

Both Dolgrim's go down, and the Gnoll's look at each other. They both fire off their bows again but move eastward and open the bronze door there. You see a small corridor leading east beyond:

Gnoll 1 Bone Bow against Cannon Attack: 7 Damage: 4 Piercing

Gnoll 2 Bone Bow against Cannon Attack: 20 Damage: 9 Piercing

You all are up, the Gnolls have moved slightly further away, but are still within 30ft.

Elero winces as the gnoll's shot completely dissipates the Protector Cannon's energy shield, but breathes a sigh of relief to see the Cannon itself is undamaged by that shot (I double-checked, and the Cannon shields itself every time it pulses out temp HP, too).  He turns, frowns at Gnoll 2 and brandishes his Light Crossbow.

Ranged attack: 21 to hit and 6 damage

The Protector Cannon will renew its energy shield, granting itself and anyone who wants them 8 temp HP.

Erix has his animals attack, taking out a ball of fur and throwing it on the ground to help aswell

Ball of fur: 4-> Boar

The boar charges forward and than hits with his Tusk

To hit 17 for 6+3 (extra d6 due to moving at least 20ft before attack) damage and DC11 strength save or be knocked prone.,

Land beast attack to hit: (16,25)-> 25 for 14dmg (pack tactics)

Clumulk: Ferocity: 4+1=5,
Brutally charges forward and attacks the possibly prone Gnoll (Using 5 ferocity)
(25,if advantage: 12)-> Crit either way for 9 dmg. 

((@DM for me its a bit unclear currently how the ferocity works, is that just 1 action, or can he also still make his usual normal bite attack?))

Mark will line his crossbow and take his shot at the gnoll that is still up. But it was a weak shot.

Attack w/ADV: 18

Damage w/Sneak Attack: 4 + 5 = 9

(Secretfool - Your Ferocity attacks happen instead of your signature attack.)

Gnoll 2 STR Save: 9

Gnoll 2 is downed by coordinated attacks from Elero and Erix, while Clumulk and Mark catch Gnoll 1 and tie him up, stopping the remaining Gnoll from fleeing. The Gnoll spins around and snarls at Clumulk, lashing out with it's teeth:

Rend against Clumulk Attack: 8 Damage: 7 Piercing

You all are up, the last Gnoll fighting Clumulk is pretty injured and fighting to the last.

Mark will want to try to interagate the last Gnoll, "Where are your bosses? What are they doing with these monsters?"

Mark DC 20 Persuasion check: 6

The gnoll completely ignores your question as he wrestles with Clumulk.

You all are still up.

The animals keep on attacking

Clumulk: (10,10)->10
Land beast: (22,22)->22 for 12dmg
Boar: (20,4)->20 for 3 dmg
While Erix Thorn whips the Gnoll
26 for 6 dmg

Seeing that his companions have things in hand, Elero casts Mending on the Protector Cannon to bring it back to full HP.

The gnoll goes down under continued assault by Erix and his companions. Eight alcoves in the walls each hold odd-looking statues of green stone in various poses. You see the corridor leading east, as well as the door remaining doors either side of that one leading northward and southward.

After mending his cannon, Elero would like to inspect the statues, to see if he can discover what they represent.

The eight niches in the walls around the rotunda contain statues. All are of humanoids, but their hands and heads are broken off and lie smashed on the floor. Seven of the statues’ stone heads have been replaced with the severed heads of various humanoids— several humans, a goblin, a blue skinned dwarf, an elf, and another alien seeming creature with sharp teeth and green mottled skin.

Elero DC 15 Religion Roll: 5

You know nothing else about the statues.

Except the severed heads are gross.  Do they look like they were placed there recently?  How rotted are the heads?  Are any of them the heads of beings we know, or have recently interacted with?