6
\$\begingroup\$

Since Gelatinous Cubes have the transparent trait, do you need to do an action perception check to spot it or you could use your passive perception?

Transparent trait: Even when the cube is in plain sight, it takes a successful DC 15 Wisdom (Perception) check to spot a cube that has neither moved nor attacked. A creature that tries to enter the cube's space while unaware of the cube is surprised by the cube.

\$\endgroup\$

3 Answers 3

5
\$\begingroup\$

It's up to the DM

Whether or not to ask your players to do an active check or just use their passive is up to the DM to determine. The only direct answer is if the player says they are looking for something, in which case, you can have them do an active check for something they are actively doing.

Otherwise, using a passive score or asking for a player to do an active check is purely up to the DM and there is no direct rule regarding this.

Either way, monsters are also here to tell a story and not just be a bag of XP. It's okay for players to stumble into it, that's why it's in the stat block! But if you want to as DM, you can also try and provide some clues that something is amiss. If they ask you to do a check, then you can have them do a check.

\$\endgroup\$
6
  • 1
    \$\begingroup\$ What if the DM dont use the passive score (which is higher than the stealth of the cube) and let the player walk into the cube without asking the player to do an active check, is that a mistake on the DM part? Thank. \$\endgroup\$
    – ordi
    Mar 29, 2020 at 20:22
  • 2
    \$\begingroup\$ @ordi don’t ask questions is comments please. Ask another question. There’s no charge for questions so ask as many as you like. \$\endgroup\$
    – Dale M
    Mar 29, 2020 at 20:26
  • 4
    \$\begingroup\$ @DaleM This is directly related to the original question and is asking for clarification from the answer, it is perfectly fine as a comment. \$\endgroup\$ Mar 30, 2020 at 0:00
  • \$\begingroup\$ @RevenantBacon No, the question is about if you need active or passive perception to spot a gelatinous cube. The comment is about when a DM should call for an active perception check. \$\endgroup\$
    – Dale M
    Mar 30, 2020 at 0:32
  • 1
    \$\begingroup\$ It might merit editing the original question, but the operative phrase is 'directly related' (which I think it is) not 'identical.' \$\endgroup\$
    – Novak
    Mar 30, 2020 at 6:06
1
\$\begingroup\$

What the Transparent trait means:

Normally, a creature cannot hide in plain sight. The transparent trait allows the creature to be hidden "even when" in plain sight.

What Passive Perception means:

DMs can use passive perception when they want to secretly determine whether the characters succeed at noticing a hidden monster.

If a DM wants to secretly determine whether a character notices a hidden gelatinous cube, then apply passive perception. If the DM is not secretly determining whether a character notices a hidden gelatinous cube, then dice are being rolled to see if the character notices the hidden gelatinous cube, because there is still a chance the character notices the cube even if he is not searching.

Crux of the Question:

Of course, a player character can choose to use an action to actively search for signs of the presence of a gelatinous cube. But the question here is whether a player character needs to spend an action to notice the cube.

Answer to the Question:

The answer is: no, not necessarily, meaning that a player character gets an initial chance to notice the cube without having to spend an action. A player character could use passive perception to notice a gelatinous cube. By RAW, the DM uses passive perception to replace a roll, meaning that if the DM is not using passive perception, then the DM is using a roll (that does not require an action) to give the player character a chance to notice the cube without searching for it.

Example: Player character Apdog has +5 perception. Player character Dojomon has +2 perception. Player chracter Merkle has a -1 perception.

Merkle is following Apdog as he walks down an open corrodor containing a gelatinous cube. The DM wants to secretly determine if Apdog notices the gelatinous cube. Apdog's passive perception is 15 which is enough to pass the DC 15 check to notice the gelatinous cube. Apdog notices the cube and opts not to walk into it. Merkle's passive perception is 9, so Merkle fails to notice the cube... however, since Merkle is following Apdog, Merkle stops and also does not walk into the cube. The cube does not move or attack, and Merkle still can't see the cube. Apdog tells Merkle something is there and Merkle decides to actively search for it. Merkle uses an action and rolls 13-1 = 12. Still not enough. Merkle can't see the cube!

But wait... Dojomon is walking down the same open corrodor but from the opposite direction, traveling to meet up with Apdog and Merkle. Dojomon is not searching. The DM decides to roll openly to see if Dojomon notices the cube instead of secretly determining if Dojomon notices the cube using passive perception (because reasons, suffice it to say the DM wants this roll to be made openly for all the players to see). The DM calls for an open roll and if Dojomon rolls high enough he will notice the cube and not walk into it, but if Dojomon rolls low enough he will fail to notice the cube and walk into it. Dojomon rolls a 12 +2 = 14, which is not enough to beat the DC of 15. Dojomon walks into the cube!

\$\endgroup\$
5
  • 1
    \$\begingroup\$ @Kirt to clarify, your position is that the DM has to use characters' passive perception to determine whether the characters notice the cube, and is not allowed to make the scenario such that the characters do not notice the cube even when their PP is higher than the cube's stealth? \$\endgroup\$
    – justhalf
    Dec 25, 2023 at 11:07
  • \$\begingroup\$ @justhalf No and no, actually. (1) Any time the character is actively looking for danger (which is all the time they are not engaged in another task that demands their attention) a Perception check is called for. The DM decides in each case whether that is active or passive. Cf. here, here, and here. (2) If the DM ruled that a passive check was called for, and PP>Stealth, the character should see the GC - to not rule so would invoke Rule 0. \$\endgroup\$
    – Kirt
    Dec 25, 2023 at 16:30
  • 1
    \$\begingroup\$ Well, then you agree to the other answer, in that DM decides whether it's active or passive? \$\endgroup\$
    – justhalf
    Dec 26, 2023 at 5:16
  • 1
    \$\begingroup\$ @justhalf Sorry, you didn't tag me, so I am just now seeing this. I agree with NautArch's answer that the DM decides whether the check is active or passive. He also seems to be saying that if the player says their PC are actively looking, the check should be active. The wording is a bit muddled, so I am not sure if that is what he is saying. If it is, I don't agree with that. The DM always decides, regardless of what the player says their character is doing. \$\endgroup\$
    – Kirt
    Dec 29, 2023 at 7:15
  • \$\begingroup\$ @CommentWanderer You already had my +1, but I do think it is improved now. Well done! \$\endgroup\$
    – Kirt
    Dec 30, 2023 at 2:44
-2
\$\begingroup\$

A Gelatinous Cube, unless newly 'spawned', would have items floating inside it that the Cube could not, and cannot digest. Clothing, flesh, leather armors, strapping, belts, shoes (unless horseshoes), in fact anything 'organic' will be consumed, but most metals and magic items will not be 'consumed' by the Cube. Thus, a gelatinous cube filling a 10-foot wide corridor will, in the VAST majority of cases, have items floating within its body. So, seeing items seemingly floating in the air will 'give away' that the cube is there. Also, things recently enveloped by the cube, will be only partially consumed, and again, be a 'tip off' of the cube's nature.

\$\endgroup\$
2
  • 3
    \$\begingroup\$ While a DM could certainly decide to run the cube like this, and many illustrations show cubes thusly (including the current official illustration), there is nothing in the cube's stat block to indicate this, and it runs contrary to the Transparent trait that is in its stat block, as cited by OP. \$\endgroup\$
    – Kirt
    Dec 29, 2023 at 7:21
  • \$\begingroup\$ From review: I think this answer is wrong, but not delete-worthy. \$\endgroup\$
    – Mołot
    Dec 30, 2023 at 2:35

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .