Chapter 2: The Gorgon Queen's Lair

Chironides whispers some instructions to the Ranger…. "We need to get the others up…go hide. Ill try to distract her long enough so you can slip back inside. Each of those heroes has a powerful healing draught. If we are not too late we can still save them and may yet claim victory"

Chironides bangs his shield and launches a barrage of magic missiles at the horror before giving a taunting laugh!

"HA HA You are such a fool Hythonia!"

Chriron takes his second wind and if Hythonia pursues ducks back out and heads deep into the western more narrow corridor.

Chiron considers the swim but then decides a minute or 2 is too long for to fallen heroes…. Chirong grips his his magic hammer 2-handed to smash through the masonry around the door in an attempt to make a hole large enough to fire through. (does not want to expose himself to a fully opned door)All Purpose tool is in the form of a mason tool which gives Chiron Profiency in Mason tools

Hands the ranger 2 flasks of Alchemist Fire "Think you hit the floor in front of her if she opens up?"

I interpreted the "go hide. i'll distract her long enough you can slip back inside" as "go inside now while I distract her and hide". This means both he would not be riding you at this time and he would be inside while you are outside. We can retcon this once, but since this is text based clarity is king.

As for breaking through the wall, the DMG isn't very helpful. It mostly just summarizes to "stone has 17 AC and large resilient structures have 27 (5d10) hit points, oh and it might have a damage threshold". A lot of DMs i've heard of use the spell wall of stone to simulate well made stone walls. Under that language, the wall is likely 5 feet thick (to hold such heavy doors) at least and thus has an AC of 15 and 150 hit points (30 * 5). The first option seems a little weak to me, so i'll go with the 2nd.

Assuming you use the warhammer and use extra attack to attack twice per round and deal double damage from the feature of the mason's tools, it would take an average of 4 rounds to break through a section of the wall (42 dmg per round, 150/42 = roughly 3.5). Booming blade does less than extra attack so I'd assume that. Based on how loud that would be, I'd say round 1 she doesn't hear it, round 2 she hears it, round 3 she realizes what that means and probably does something, and round 4 you break through.

Thoughts on both topics?

Ok, since it will take a couple rounds, this will give Omeros some time to act, so let's see what he's doing in the meantime.

More suicidal moves. Omeros tried to climb out of the water and hide behind a pillar.

Omeros falls back in the water, with a loud splash. Hythonia looks over where the sound came from, but Omeros was able to dive deep enough that she did not spot him.

Chironides begins breaking through the wall. For now, only he knows this is happening (3 rounds to breakthrough. Next round Hythonia starts hearing Chironides work).

And Kadmos dies in a heap on the floor, a failure to the King and to Iroas.

It seemed almost impossible: climb and be seen or fall and be unseen. Perhaps falling and being seen was the best way to go. If any others lived, perhaps Omeros could give them a chance at avenging him.

"Erebos take you, harridan!" Omeros spat back, defiantly refusing her offer!

"See me, Hythonia! Feel the wrath of Omeros! Feel the storm of Keranos!"

Blazing Invictus fired three force beams while one of the stars orbiting Omeros flew at Hythonia!

The first beam of Omeros's eldrtich blast hits Hythonia in the forehead and she yells in anger. The second looks to be an even cleaner shot, but the poison makes Omeros hold his stomach just as he aims and it goes wild. The second does the same, but he focuses long enough to fire the crown of stars mote and hits Hythonia in the chest. Hythonia reals back, surprised to get hurt so much in a small amount of time.

Chironides continues his bashing of the wall. He sees a small glimmer of light, but not enough for anything to fire through. He knows he will have a hole on his next turn.

Hythonia, looks at Omeros in pure anger, with a small hint of fear.