Nuzej continues to focus on the Phylactery location spell.  He has a firm feeling that this crystal skull is not the phylactery, but that the phylactery is somewhere down and forward a bit more from this room. 

Nuzej says, "this is not the crystal skull's domain. Our target lies further on. Down, and forward. Does anyone wish to scout, or should we walk? If someone can scan for signs of the arcane, that would be prudent."

He looks for any kind of trap sign on their path forward.

Investigation: 18

Simaal reports to the group if he sees any changes in the last room he stopped. "I'll let you know if I notice anything, albeit magic detection is really beyond my capability for the most part."

Thyrius had been silent since landing in the central island and until reaching the crystal skull cave. His mind was busy taking in all the details around him. He wondered if his familiarity with the dead gave him any insight into what the charm markings may mean.

-> Arcana check, since his familiarity comes from his warlock-ness (or would it be warlock-itude)? Religion or History use the same meager modifier. Here goes nothing: 3

"Down and forward?" Thyrius mentally asks everyone, but particularly Nuzej. "Do you mean within the bone pool?"

There is no other exit from this large chamber, so indeed, Nuzej seems to be indicating that it is below the "bone pool" somewhere.  Though, he seems to be looking around the room a bit confused as if trying to figure out if there's another way to go.  It seems obvious though that it must be beneath the bones.  

As for the Talisman's, yes indeed. Despite having come from literally, worlds away, across the multi-verse, Thyrius examines the talismans closely and sees sharp similarities to primitive tribes, as well as from his instinctual knowledge of those that worship the dead. Much like Thyrius' own link with his patron....the people here seem to worship this crystal skull....or at least whatever they represent. The talismans are offerings...including bundles of hair, or tied up teeth, or bits of dried flesh that bind the worshippers to their patron. This patron it seems clear protects and is worshipped by some primitive tribes. It's also clear that they offer more than bits of themselves, based on the pool of bones and the dried blood at its edge.

Over the link again, Nuzej says, "Do we dig, under the bones? Surely there is no trap or hidden danger lying in wait, protecting a lich's valuables. Perhaps there is a triggering switch of some kind. Or a passphrase we'd have to guess, that would move all the bones away. I could try to push myself or most of us into etherealness to scout around in there. I could reverse gravity after we secure ourselves to something and watch the bones fall to the ceiling. I can't do many of those, especially if we want to be able to teleport away. I could try to excavate using Bigby's Hand or telekinesis. All of these things, save going ethereal, will make me lose my connection to the phylactery. I value your counsel, but will make my own decision."

He tries a simple mold earth at the edge of the bonefield to see if the magic works to manipulate and excavate them. 

"Etherial plane sounds like the best option! We can pass the traps this way and clearly see the path if there is one. If you can do it - please, do." If they were not about to smash everything around, safe exploration looked like a good idea.

 Thyrius agreed with Mirica: "Yes, and it also reduces the chances that we'll be sensed by some creature or trigger magical and mechanical traps. Keep your link to the phylactery, Nuzej, and lead our ethereal forms through the bones and directly to the artifact. If need be, I can look through the solid bones once we are close in the same way I looked through the rubble back in Ythrin to find a corpse within the fallen, frozen-solid tower."

"We could head down that thin walkway to the southeast wall where there's a cave entrance. Being thrown into the water would be hazardous, and likely one of the defenses of this place."

Nuzej attempts a mold earth, but the hard rock of the cave doesn't respond, not that he was expecting to. It was worth a try but was ineffective. 

Toc shrugs, "If Nuzej makes us ethereal, it certainly has the chance to simplify this journey. Though I doubt his connection to the phylactery will work while we are ethereal, since we will technically have crossed a planar boundary." 

"Hold up, I'll just scout it out" says Simaal mentally. He lets the group know what he sees through the sensor that is entering the bone pile and looking for a way down. "Fascinating... the bones are fused together that there are no real gaps. Have to try something else, please stand by."

"Not all of us need to step into the ethereal plane then," Thyrius responds. "Perhaps Nuzej can hover above the bones and stop at the spot where he identifies as being in perfect vertical alignment with the artifact. Then, those who are ethereal can simply dive in."

While the group consider it, Thyrius shares what he had learned from the many talismans and charms.

Simaal doesn't find any evidence of the bones being 'fused' together. But certainly the pile of bones doesn't have any 'tunnels' through them that are big enough to fit even the nut sized magical eye. However, this limitation doesn't seem to bother Simaal. He takes a moment to 'try harder'...and describes to the group.  The eye presses down through the bones...perhaps 10 feet thick worth....enough to easily bury a person standing up, and then presses through and emerges beneath the bones into....a large dark watery cave.  Some force above seems to be keeping the bones from simply sinking into this black watery grave. The water around Simaal's mental eye seems to be a natural underwater domain, pure clear water that his dark vision lets him peer about as he slowly drift downwards towards the rough bottom. The zip of small dark shadows through the water catch the edge of his mental vision as fish flick to and fro in the dark. The bottom of the cave is filled with a uniform layer of silt, but as his eye nears it he see bones jabbing up from the muck.

Simaal's magic eye moves about the watery domain. It doesn't take him long. Just ahead about 60 feet, and settled at the bottom of the underwater cave is what looks to be a small shrine carved into. rocky outcropping.  Runes of magic are carved into the rock around the small shrine. What looks like a glass jar with a clamped on lid sits in front of the shrine, apparently half filled with sand. Several gems, several piles of coins, and a several other items of interest sit scattered about the area. What appears to be a partially re-constructed skeletal body lays before the shrine. The bones of the body look half-formed......thin and fragile. 

Simaal mentions "It's possible we can bypass these bones if we go the wrong way, please standby." Simaal moves his eye back out then moves it back towards the tree then back to the north passage in the half cave in water, then enters the water and tries to get back to under the bones about 30 using the shaft of light as a guide to get back to the underwater grave. Uhm... that said... it could just be connected to the lake where the tree is at, so he'll try there first to see if they're connected.

That light is fake news.  I found a picture of an underwater cave that’s fully dark, but, it wasn’t much to look at. (Black screen)

Simaal pokes around with his mental eye but doesn’t find any route connecting the two realms. 

Nuzej asks if the floor between this chamber and the pool seems thicker than 5 feet. If so he could shape the stone to provide an entry point.

Indeed, there doesn’t appear to be a floor. The bones appear to be resting on the top of the water somehow. 

"Other than mining my way in the ground with a pick axe, I have no other means to get through the not-fused-but-super-close-to-each-other bones." Simaal backs off in case he got to be walking on the bones which he would have avoided.

If Simaal shared his findings, Mirica´s suggestion would be for someone use Etherial spell to get inside, grab all in the srine (or at least smash those bones), return to etherial space and then to the group.

Looked more simple than digging through.

Thyrius once again agreed with Mirica, reiterating his recent point about only a portion of the group going ethereal. "Perhaps the spell could be cast on everyone, but Nuzej stays in the material plan so he can tell us where the phylactery is." Then:

Option 1: Some go into the lake, others stay up. Should something go wrong underwater, the cavalry can come in while also avoiding the bones, or the divers can escape back up so everyone has a chance to attack any pursuers, including Nuzej.

Option 2: Everyone goes ethereal and passes by the bones and into the underwater lake. Then, while underwater and able to breath unhindered due to Toc's spell, Nuzej pops back into the material plane so he can tell once again where exactly the phylactery is. Should anything go wrong, Nuzej goes ethereal again and we all escape as needed.