The party meet on Kylal by the Kyholt-Beachhead gate where they are briefed by Dr East Wind, a Vyixian archaeologist from the Zeitgeist Experimental Keter Exploration Division who explains the mission: to enter the unexplored levels of the Beachhead installation and find out what's down there. The party and Dr Wind discuss the current state of the Beachhead and its stone guardians, and Blue Five is very interested to try to communicate with the stone guardians but is unable to do so as they communicate in their own method.
They head into the depths and encounter new five-limbed stone guardians that prove hostile. These ones - designed with blades and armour - are more aggressive than the ones they've met but the party dispatch them and Blue Five augments one of their shields into shielding for themselves. In doing so the pentagonal and five-sided patterns of the place get into their mind a bit and they become enthused by the number five at the same time that their Mystic companion calls down an Intervention to allow them to communicate with the Pentagonal beings.
They continue through a decontamination shower - avoiding being decontaminated - and descend down into the depths. As they go they find the desiccated remains of one of the pentagonal species clutching a tablet. When they take the tablet they are suddenly set upon by Decay which they fend off before reading the carved tablet using their Ship Heart given ability to comprehend:
New Information
Objective Achieved
Sleep Eternally
Sacrifice Worthwhile
No Further Advice
They push on, solving a puzzle that seems to tell the story of the five-limbed species turning other species into themselves, and descend into a large chamber where there are spindly five limbed creatures tending to a large pentagonal box in the middle. There are five doors to the room, including the one they came through, and they find they are all sealed save for the one they entered through and one ajar at the other end of the room. The doors are labelled:
They enter Deliberation and become part of a simulation of a planet waging war on other planets. They recognise none of the planets but their planet is victorious. As the simulation ends they find themselves speaking to a very large stone guardian that refers to itself as the Custodian and is confused about where and when it is, and the status of its work (“Custodial” in nature). The party tiptoe around the fact they've not arrived at “the initial destination” as the Custodian calls it, and determine that the Custodian calls the planet of Kylal its home and that the crypts contain the ancient civilisation's members as “passengers” of the planet being moved to another star system over a very long period of time. Upon giving up the information that the planet has not in fact reached its destination proper yet, the Custodian decides to awaken “the Supervisor” for further instructions.
The party continue to press the Custodian for information as they also call in Dr Wind for advice. Dr Wind is flustered and unsure and's only idea is that because this isn't on Kylal it may in fact be fine to proceed. They eventually roll a die to see whether they advise opening the sarcophagus or not, and suggest opening it. During the call, Blind Rising reads out the inscription and the Custodian becomes concerned by the mention of “No Further Advice”.
The Custodian describes “No Further Advice” as terrorists who have acted and, seemingly, succeeded in their sabotage. The Custodian becomes even more concerned with reviving the Supervisor and enlists the party to help as the systems come online. The party attempt to interfere with the sarcophagus but its systems are beyond their successful sabotage. They help open the sarcophagus but when it opens the resident falls out very much dead and has been for some time. The party attempt, with partial success, to avoid the clouds of toxic spores that emanate from the sarcophagus and take the treasures clutched in the supervisor's hands (a brass orb and an ornate knife) before the sarcophagus begins to decay and attack them.
The party fend off the Decay and consult with the Custodian who is horrified to discover that Decay occurred. It refers to the Decay as “the problem” and insists that its owners had eradicated it. It determines need for further Deliberation and asks the party to leave so it can secure its facility. It refers to Blue Five as their means of future access and then sends them on their way.
Back at the base camp in Beachhead the party can see only the lower facility is now sealed off by the Custodian, not the whole place, and debrief to Dr Wind about the mission. They realise they can now talk to the Stone Guardians but as they do the ability starts to fade, so Blind Rising infodumps everything possible onto it. Dr Wind is fascinated and takes the “enlightened” Crypt Guardian off for further investigation.