Quote from drumdigby >>

Zoveldra prepares a punch for any Gargoyle that gets close, but the gargoyles only lower themselves 30ft on their turn and take the Dodge action.

Anyone’s spells go off when this happens? Zoveldra’s punch certainly doesn’t.

 (Apologies, Christmas celebration had me unable to reply in time.)

LANDMOPs Shadow tendrils would reach the gargoyles. Making an attack at disadvantage

Attack: 11 Damage: 9

LANDMOP makes a shadow tendrils attack against the Elemental

Attack: 13 Damage: 9

Moving within 30 feet if needed, or out to 30ft if in melee

"That's a lot of little rocks," Elero mutters, then picks up a stone. "Here," he says, "have one more."

He casts Catapult at 2nd level, spinning the stone through the curved metal of his Arcane Firearm and then hurling it at the Elemental.  It must make a DEX 15 Save or take 16 bludgeoning damage, plus an extra 4 for Arcane Firearm.

As a bonus action, the Protector Cannon gives 6 temp HP to all nearby allies.

Earth Elemental DEX Save: 17

LANDMOP is quite far away from the Elemental so would need to aim their spell at the Garloyle, it misses. Elero’s Catapult hits the Elemental, while Zoveldra uses all her movement to get into melee with the Elemental. Erix is able to get a thorn whip on a gargoyle and pull it closer.

The gargoyles all fly in, then fly back out 30ft, attacking Erix, Elero, and LANDMOP; while the Earth Elemental attacks Zoveldra:

Claw against Erix Attack: 22 Damage: 6 Slashing

Claw against Erix Attack: 10 Damage: 8 Slashing

Claw against Elero Attack: 7 Damage: 9 Slashing

Claw against Elero Attack: 10 Damage: 8 Slashing

Claw against LANDMOP Attack: 5 Damage: 4 Slashing

Claw against LANDMOP Attack: 14 Damage: 4 Slashing

Claw against LANDMOP Attack: 20 Damage: 5 Slashing

Claw against LANDMOP Attack: 21 Damage: 5 Slashing

Slam against Zoveldra Attack: 17 Damage: 14 Bludgeoning

Slam against Zoveldra Attack: 23 Damage: 21 Bludgeoning

You all are up, Zoveldra is in melee with the Elemental, while the gargoyles harass from the sky.

((@Dm can I cast conjure animals for 2 giant eagles as I can't find a rating 2 flying animal?))

Elero eyes the elemental's structure more closely, and tries a different tack. "Time to break these rocks," he says, and casts Shatter at 2nd level.  The elemental must make a CON 15 save or take 16 thunder damage, plus 7 for the Arcane Firearm, or half as much if it succeeds.  Since it's made of stone, it has disadvantage on the save, and it's vulnerable to thunder damage, so the damage is doubled.

As a Bonus Action, the Protector Cannon pulses out 6 temp HP to any who need it.

I believe the Quetzalcoatlus is a flying dinosaur at CR 2

Ah right, didnt think dinos were valid^^

Erix casts conjure animals to spring forth a Quetzalcoatlus 30ft of one of the Gargoyles. His other animals will ready attacks for gargoyles getting in range again, Erix hopes focussing on the gargoyles will release the earth Elemental from its corruption.

The Quetz attacks one gargoyle: with a flyby from 30ft so 3d6 extra damage.

to hit 12 for 23dmg

Also, Shatter has a 60-foot range and it's a 10-foot sphere of effect, so if possible Elero would like to target a point behind the Elemental, or something that's far enough away to not catch Zoveldra in the blast radius.

Earth Elemental CON Save: 18

Elero shatters the Earth Elemental, it manages to avoid some of the damage, but it does seem effected by the spell. Erix' huge summoned dinosaur is unable to hit Gargoyle 1, but it's huge form in the cavern is quite impressive. Zoveldra punches a few rocks off the Earth Elemental, but LANDMOP misses one of the Gargoyle's with Blood Bolt. Erix' Thorn Whip hits one of the Gargoyle's as they go in for an attack against you all. The Earth Elemental attacks Zoveldra:

Claw against Quetzalcoatlus Attack: 23 Damage: 6 Slashing

Claw against Quetzalcoatlus Attack: 20 Damage: 9 Slashing

Claw against Clumulk Attack: 15 Damage: 8 Slashing

Claw against Clumulk Attack: 10 Damage: 5 Slashing

Claw against Erix Attack: 22 Damage: 9 Slashing

Claw against Erix Attack: 13 Damage: 9 Slashing

Claw against LANDMOP Attack: 16 Damage: 8 Slashing

Claw against LANDMOP Attack: 13 Damage: 5 Slashing

Slam against Zoveldra Attack: 28 Damage: 22 Bludgeoning

Slam against Zoveldra Attack: 22 Damage: 11 Bludgeoning

You all are up. The Earth Elemental fights Zoveldra as the Gargoyle's fly in from over head. One Gargoyle grapples with a huge flying dinosaur overhead.

Remember it has disadvantage on the save, since it's made of stone.

Yep that was with disadvantage. They rolled a 13 and a 14, with a +5 to CON

With the Gargoyle getting into range, Clumulk attacks it:
to hit 13 for 5dmg

Erix con save: 15, Quetz stays
Quetz goes for a gargoyle 30ft away, not getting op attacks due to flyby:

To hit 16 for 15dmg

Erix meanwhile casts another thorn whip to try and get a gargoyle within range of one of his animals:

to hit 18 for 6dmg and 10ft pull.

((I assume gargoyles used flyby again?))

(Yep the Gargoyle's are using flyby.) Erix' attack misses the Gargoyle, while the dinosaur hit's Gargoyle 1, Erix's second attack hits Gargoyle 4 and pulls it onto the ledge. Elero hits the Earth Elemental with an infused crossbow bolt, while Zoveldra bashes a few more stones off it. LANDMOP hits Gargoyle 3 with a Blood Bolt. The Gargoyle's keep up their attack, while the Earth Elemental keeps battering Zoveldra with a constant stream of insane rock slams.

Claw against Quetz Attack: 24 Damage: 13 Slashing

Claw against Quetz Attack: 5 Damage: 6 Slashing

Claw against Elero Attack: 23 Damage: 7 Slashing

Claw against Elero Attack: 24 Damage: 11 Slashing

Claw against Erix Attack: 24 Damage: 12 Slashing

Claw against Erix Attack: 7 Damage: 10 Slashing

Claw against LANDMOP Attack: 21 Damage: 8 Slashing

Claw against LANDMOP Attack: 10 Damage: 4 Slashing

Slam against Zoveldra Attack: 9 Damage: 13 Bludgeoning 

Slam against Zoveldra Attack: 18 Damage: 19 Bludgeoning 

You all are up. The Gargoyles keep flying in and out with Flyby, and while the Earth Elemental is looking beat, it still fights on.

(Trying to catch up, thanks for botting LANDMOP. I'll update hitpoints and concentration checks hopefully later today)

Elero reels from the claw attacks, but his focus stays on the Elemental.  He picks up a broken-off piece of one of the gargoyles, feeds it through his Arcane Firearm's coiled metal, and fligngs a Level 1 Catapult at the Elemental.  It must make a DEX 15 Save or take 14 bludgeoning damage plus [roll]1d8[/roll] damage for the Arcane Firearm.

As a Bonus Action, the Protector Cannon pulses out 6 temp HP of shielding to nearby allies.

Trying the Arcane Firearm d8 again: 2

Assuming LANDMOP can't get in range of the elemental with (30ft) LANDMOP will hold action for a shadow tendrils attack 

23 attack 12 cold damage