After some investigation, Elero sees this room for what it is, a decoy. This room has been made up to seem like a wizard's secret chamber, but it features nothing of any value for that purpose. Additionally, he sees a bookcase in the corner that looks very similar to the secret entrance revealed by Sarkt in the room above.

"This was designed to fool intruders, apparently.  Let's see what's beyond that bookcase, but be careful.  We should probably check it for traps or alarms before proceeding."

Mark nods and prepares his bow.

Elero Investigation check for traps: 13

Elero finds no traps or alarms on the bookcase. Are you going to push it open and head in?

Yes lets head in.

16

You all head down the stairs to a large square chamber which contains a table, a stool, odd writing implements such as four-tipped styluses and sheets of parchment, and many books and scrolls. Elero and Mark don't see anything, but Erix notices as you enter there are three humanoid shapes hiding, each behind a pillar. He recognizes them as Zaerun, Ash, and Kliz the goblin you let go back at the manor. "Now! Take out the Cannon first!" Ash yells. Erix tries to warn the other two but only succeeds gasping before the attack begins. Also, can you remind me what animals Erix has out? Initiative:

Group 1: Them

Group 2: You all

Zaerun and Kliz pull out their bows and fire two shots each at the Cannon (Zaerun will switch to Elero if the Cannon goes down.), the first being with Advantage due to being Hidden. Zaerun had a look of menace in his face, while Kliz looks terrified of you, "Sorry!" He says as he shoots at the cannon then Attempts to Hide back behind the pillar. Ash casts Hold Person on Mark, then conjures a dagger in the air and attempts to attack him with Spiritual Weapon:

Kliz Shortbow 1 against Eldritch Cannon Attack: 14 Damage: 4 Piercing plus 3 Piercing due to Advantage

Kliz Shortbow 2 against Eldritch Cannon Attack: 6 Damage: 6 Piercing

Zaerun Longbow 1 against Eldritch Cannon or Elero Attack: 18 Damage: 13 Piercing

Zaerun Longbow 1 against Eldritch Cannon or Elero Attack: 16 Damage: 8

Ash Hold Person against Mark who makes a DC 12 WIS Save or is Paralyzed: 15

Ash's Spiritual Weapon then attacks Mark, who shakes off the Paralysis. "Sarkt's sold us out the tentacles freak!"

Spirtual Weapon against Mark Attack: 6 Damage: 4 Force.

You all are up, the three attackers go back behind the pillars, all obscured. Kliz also attempts to Hide, so if he rolls over your Passive Perceptions he's hidden I tihnk. Stealth Check: 23

((Animals: Dire wolf, Boar, Clumulk, and depending if it has been an hour since the first fight: Land beast))

Erix charges forward towards Zaerun as he transforms in a Black bear.

While his animals follow and attack:

Dire wolf: (23,19)-> 23 for 11 dmg and DC13 Str save or be knocked prone.
Boar: (13,7) regardless of advantage from prone this is a 13 for 7dmg and DC11 strength save or be knocked prone
Clumulk: Ferocity: 4, sign. attack: (14,6)->14(again regardless of advantage or not)  for 3dmg
Land beast, if still available: (24,9)->24(pack tactics) for 12dmg

(I can't remember, have you completed a Short Rest yet? If so the Land Beast wouldn't be up.)

Zaerun DC 13 STR Save: 14

The Boar and Clumulk's attacks miss Zaerun, but he is now surrounded.

Elero and Mark are still up. Erix has Zaerun surrounded but Ash and Kliz still hide behind the other pillars.

I'll go last, since I'm on a road trip, and won't have the chance to get caught up until tomorrow.  Plus the cannon's still going (AC 18 is handy) so I'd like to line it up for a good blast at the end of the turn if possible.

Alrighty I'll give you and ZelocktheDragon an extra day to respond. I don't really want to bot you in the big climactic battle.

Quote from drumdigby >>

(I can't remember, have you completed a Short Rest yet? If so the Land Beast wouldn't be up.)

Zaerun DC 13 STR Save: 20

(( Only the action short rest of 5min I believe))

Mark's eyes begin to glow, then he steadies himself and shoots at the spell caster. 

B/A: Steady Shot

Damage: 5 + 7 = 12

Attack w/ adv: 6, 18

Dented, but still going, the Eldritch Cannon moves 15 feet to get a shot at the enemy behind the top-most pillar and unleashes its breath weapon.

DC 13 Dex save or take 13 fire damage.  Half as much if he saves.

Elero will move up/north to get a clear shot at the same enemy with his hand crossbow.

22 to hit and 5 damage.

Mark's crossbow bolt misses. Unfortunately, as Zaerun is surrounded by Erix' animals, the breath weapon also hits the boar.

Boar DC 13 DEX save or 13 damage, half on a save: 17

Zaerun DC 13 DEX save or 13 damage, half on a save: 13

(Actually reading the Eldritch Cannon rules, you designate the targets, so the boar takes no damage.)

Zaeron's face forms into a wolfish grin as he bears the brunt of all these attacks, he says the words "My turn" as he visibly transforms into a large humanoid-wolf hybrid with hair running down like a giant mohawk down his back, and large teeth. He bites at Erix, trying to infect him with his lupine curse, then scratches at him to end him. Ash throws a Command at Mark to drop his weapon after stabbing at him with her Spiritual Weapon, and fires two shots from the shadows again at the cannon, getting advantage on the first shot. "Sorry again" Kliz says as he does this, the goblin really seems upset that he's forced to fight you again.

Bite against Erix Attack: 21 Damage: 10 Piercing and on a hit Erix makes a DC 12 CON save or is inflicted with a werewolf curse: 15

Scratch against Erix Attack: 23 Damage: 9 Slashing

Spiritual Weapon against Mark Attack: 23 Damage: 3 Force

Command: Mark makes a DC 12 WIS Save or has to drop his weapon and end his turn next round: 2

Shortbow 1 against Eldritch Cannon Attack: 13 Damage: 4 plus 2 Piercing

Shortbow 2 against Eldritch Cannon Attack: 10 Damage: 4 Piercing