I'm new to DMing, and trying to figure out what's fair vs. fun on when the player characters have a chance to spot a gelatinous cube. So if they are in a dimly lit dungeon, when do you have the PCs roll the unmodified DC 15 spot check?
The 3.5e Monster Manual says:
Transparent (Ex): Gelatinous cubes are hard to see, even under ideal conditions, and it takes a DC 15 Spot check to notice one. Creatures who fail to notice a cube and walk into it are automatically engulfed.
In our dungeon, I had the gel.cube hiding around a corner and the PCs had to make a spot check when they rounded the corner. The guy in front made the spot and stopped everybody from just blindly walking into it and being auto-engulfed (the 3.5e rules).
To simplify the question though, let's say the PCs are walking down a 130 foot dark passageway with the gel.cube at the far end. Does the Dwarf get a spot check at 60 feet (60' max darkvision), then later a spot check for the elf when dim torchlight reaches it (I read in the 3.5 PHB pg. 16 Elves get twice the dim light vision distance as humans), then at 20-30 feet when the human/halfing is within decent torch range? Or is it so hard to spot at that distance (increasing difficulty by +4 or +8 or more on the DC due to distance and a nearly invisible unmoving gelatinous cube), that they'd have to wait till they are much closer? Or do you allow multiple spot checks per character as they get closer? My thought is wait till much closer, but what is fair and fun?
- This thread below talks about it vs. darkvision in 5e terms. I'm
playing 3.5e, so I might go with a +4 on the DC if they try to spot
it at medium range on their vision:
Is it harder to see a Gelatinous Cube with darkvision?
- This thread makes it clear that it isn't truly invisible:
When do you see a gelatinous cube?
- I feel a second question coming up about how many spot checks can you
make as you approach something hard to see from far away, but that's
bending the rules on asking questions so I'll leave this post with
this link which might answer that question for me as I go read it:
How to use spot checks in a wilderness encounter?