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Looking Over Book of Challenges: Beholder Dome

It's just cover art


A beholder has set an ambush for intruders in a self-themed room.


Similar to Cave of the Snake, I like that there are a number of doors to undefined locations left for the GM to determine.

While I’m not a big fan of the high tech feel of the descriptions since I’d think beholder design aesthetics should be more alien or bizarre rather than futuristic, I do appreciate that it’s clearly different from the typical Dungeons & Dragons design aesthetic (and yes, I am aware of S3 – Expedition to the Barrier Peaks), and the extremely smooth surfaces could imply they were carved out via disintegration.

Patterning the door traps after the standard beholder’s eye beams is a cool idea.

Unlike in Watch Your Balance, I like the simplified approach to figuring out how the floor tilts for this encounter since the calculations for the balance of a disk are much more complicated than for a center-pivoted lever.

I like that messing with the mechanism under the floor as two different check difficulties (for either locking it in its current position or returning it to the original position) and that there’s a risk of taking damage from failing by a significant margin. That’s good interactivity.

Having some delay between the floor trap’s activation and the beholder’s entrance is a good way of presenting a gradual escalation of danger instead of dumping everything on the players at once.

The advice for scaling down the challenge (remove the ray traps and use incorporeal creatures in place of the beholder) provides a decent basis for reworking the encounter to suit other creatures, though the overall room design and tilting floor might raise questions if left as-is.


The boxed text describes the initial door as “featureless”, only to be contradicted by the subsequent description mentioning a flush circular button where the handle would be. I’d skip asking for a Search check and just mention the circle. It should be rather easy to spot, given that the door is polished “to an almost mirrorlike finish” (even shallow scratches tend to be very noticeable are on mirror-finish metal).

Likewise for searching for the doors inside of the dome.

The text descriptions and map dimensions don’t match. I’d double the map scale to match the text.

I’m not a fan of needing to make an attack roll for the ray traps and then still allowing a saving throw to negate/resist. I prefer the approach of letting a ray go along its path until someone/something fails to save against it or it reaches its maximum range.

The boxed text for locking the doors should mention them closing first (as the preceding text does).

As with Watch Your Balance, the writer overestimates how difficult it is to move on a slope. While it’s somewhat less egregious here because the polished metal floor would provide less traction than a typical stone surface, I’d opt to treat any tilt of 10° or less as simple difficult terrain (which also gives a warning period before the PCs need to start making checks to act at all).

In general, “roll a check to be allowed to take a turn” design leads to a very negative play experience, even if nobody fails any checks. I’d change it to allowing the player a choice between using Balance (to move normally, falling/sliding on failure) or Climb (to move by crawling, being unable to move but still allowed to act from a prone position on failure).

In addition to returning the platform to its original position, I’d allow the DC 35 check to set it to any position of the PC’s choosing with the same 5°/round rate of change.


I’m not sure why the write-up says “[a]n insidious Dungeon Master should think about where the eleven exits from the Beholder Dome lead”. Should a normal GM have them lead into the void beyond creation? That can hardly be the case when a later part says each door “opens into a corridor leading into another area of the dungeon”.

Having used lights inside of stainless steel chambers/vessels that were much more confined than the dome, I’m pretty sure light reflections don’t work the way the author thought they do. It gets bright, but it’s nothing like looking next to the sun.

The ray traps are described as going off “[w]hen a door is opened for the first time”, but there’s no indication of how long they take to reset. Given that the dead adventurers are implied to have been killed by the traps yet all of the traps are active when the party arrives, they’d need to reset at some point.

The telekinesis trap says it lifts its victims up “to 100’ ceiling, then drops [them] for 10d6 damage”, but the dome has a radius of only 50’ (assuming the map’s scale is doubled), so it’s impossible for someone to fall that far unless they can go through the floor and the mechanisms supporting it while still taking damage from hitting the bottom of the sphere.

When something is described as being “actually mechanical, based on a system of magnets and counterweights”, that usually means the writer wanted to avoid making it magical (since there are abilities like the beholder’s central eye that could interfere with a magical contraption) without bothering to figure out how to actually make it work. It’d be better to just admit that it works by Hand Wave.

Explaining what the inside of a sphere looks like is insulting to my intelligence.

Describing the mechanism under the floor as “whirring gears and cogs” in the same section that started by describing it as “a system of magnets and counterweights” is a consistency oversight that makes my guess about the latter having been a Hand Wave feel even more likely.

The boxed text for the beholder’s entrance is presented like an uninterruptible cut scene in a video game. It’s also not clear how the beholder can even open the door when the previous section said they were all locked for another 59 minutes and 42 seconds (the answer can’t be that the beholder’s central eye is suppressing a magical lock because it’s described as using that eye to prevent the ray trap beyond the door from activating when the door opens, hence why it enters moving backwards).

The “Tactics” sections says nothing of any real value.

The treasure is the usual boring combination of currency, mathemagical equipment, and healing potions. Maybe the fact that so many encounters in this book have corpses of former adventurers with such things is meant to indicate that the players should value more interesting magic items, since the adventurers with those end up surviving?

The advice for scaling up the challenge is just to add another beholder.


Beholders are almost always near the top of the list when it comes to people’s favorite original Dungeons & Dragons creatures, so it’s to be expected that this book included an encounter built around one. For extra flavor, the ray traps fit in thematically (and I’d advocate for using them elsewhere in the dungeon, too), as does having a tilting floor inside a sphere to torment earthbound weaklings.

While the encounter write-up itself is fairly complete, it’s important to remember that it requires detailing what exists beyond twelve doorways (including the entrance) and that a hidden part of running a beholder is roleplaying a near-genius yet utterly alien creature (in terms of both social presentation and tactical decision-making). Thus, there’s a substantial amount of work expected from a GM who wants to use this encounter, and that’s without even considering further issues like how hostile is the beholder by default, should this particular beholder have different eye rays from usual, are there opportunities for the PCs to learn about its powers before running into it, why are the PCs even interested in exploring this area, etc.

That all said, there are similar issues to be addressed when it comes to using most creatures on the higher end of the power scale, and there’s more that I like about this encounter than not. I’d say the only major problem is figuring out how the beholder is able to enter the dome while the doors are locked; everything else is fairly minor (picking a cooldown duration for the ray traps, deciding which approach to take for how the mechanism under the floor works, and replacing the treasures with more interesting ones).

All in all, this is a pretty cool encounter for an iconic monster. It expects a good bit of effort from the GM to flesh out the greater context, but aside from that, it’s hardly fair to expect much more.


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