Interestingly enough if you look back in previous editions they're a little better: things like magic mouth are specifically described to rely on sight and the like.
However what's really needed is a comprehensive breakdown of what the sensor can perceive. And that can't be too broad either:At present glyph of warding is one of the few ways in the game to detect someone's alignment. Technically it could be one of the most powerful divination spells in the entire game if you don't make up limits on what it can know ("This glyph triggers if bob the necromancer goes out and leaves his spellbook unguarded", "This glyph triggers if the artifact of whosit is within 10 miles")
Yeah, I was looking back to AD&D's
glyph of warding recently, and I underlined everything that clarifies the trigger.
[SECTION]
Glyph of Warding (AD&D)
A Glyph of Warding is a powerful
inscription magically drawn to prevent unauthorized or hostile creatures from passing, entering, or opening. It can be used to guard a small bridge, ward an entry, or as a trap on a chest or box. When the spell is cast, the cleric weaves a tracery of
faintly glowing lines around the warding sigil. For every square foot of area to be protected, 1 segment of time is required to trace the warding lines from the glyph, plus the initial segment during which the sigil itself is traced. A maximum of a 5' X 5' area per level can be warded. When the spell is completed, the glyph and tracery become invisible, but
any creature touching the protected area without first speaking the name of the glyph the cleric has used to serve as a ward will be subject to the magic it stores. Saving throws apply, and will either reduce effects by one-half or negate them according to the glyph employed. The cleric must use incense to trace this spell, and then sprinkle the area with powdered diamond (at least 2,000 g.p. worth) if it exceeds 50 square feet. Typical glyphs shock for 2 points of electrical damage per level of the spell caster, explode for a like amount of fire damage, paralyze, blind, or even drain a life energy level (if the cleric is of high enough level to cast this glyph).[/SECTION]
Then 3e expanded that to include a host of other triggers, which I think in retrospect was a mistake because it muddies the waters of what is actually happening in the narrative.
[SECTION]
Glyph of Warding (3e)
You set the conditions of the ward. Typically, any creature entering the warded area or opening the warded object
without speaking a password (which you set when casting the spell) is subject to the magic it stores. Alternatively or in addition to a password trigger,
glyphs can be set according to physical characteristics (such as height or weight) or creature type, subtype, or kind. Glyphs can also be set with respect to good, evil, law, or chaos, or to pass those of your religion. They cannot be set according to class, Hit Dice, or level. Glyphs respond to invisible creatures normally but are not triggered by those who travel past them ethereally. Multiple glyphs cannot be cast on the same area. However, if a cabinet has three drawers, each can be separately warded.[/SECTION]
5e continues with 3e's trend but only exacerbates the problem.
What's great about the AD&D version is there is little ambiguity for the DM about how to narrate it. The trap is invisible, but if detected appears as faint glowing lines, and a magic word allows one to move through the ward without triggering it. So the trap has a vulnerability that players can exploit – if they learn about the presence of a glyph (e.g. reading old manuscripts, talking to dungeon inhabitants, casting detect magic), then they have the option to try and learn its password. That might involve finding a certain dungeon inhabitant to interrogate or going through their notes/spellbook. It might involve casting a divination. Or, a really clever PC might be able to deduce the password from what they know about the caster and the warded object/area.
And maybe that should be how the
magical inscription trigger works in D&D. Inscriptions are about
the word, and so it makes sense that a password can overcome them.
What I like about this approach is that it opens up the door for more creative countermeasures. Maybe there can be a magic quill that in the hands of someone with fine motor skills and 5 minutes of time could actually change a magical inscription, so a successful Sleight of Hand check using such a magic quill could slightly change the password or slightly change the effect of the glyph.
Unfortunately the game has been mostly constructed so that poison and disease are fairly irrelevant, with the possible exception of 1st level parties with no paladin.
Yeah, it's not that poisons just got the shaft in 5e, but they also are designed to mostly be one-and-done. I agree they should be scarier, but even more than that I think it's a mistake to treat most poisons as an instantaneous damage vector. There really ought to be an onset time – even if it's just a round – because that gives the players a decision point. The problem with D&D's "gotcha" traps/poisons is that they are designed without interesting decision points in mind.
In fact, with
glyph of warding, I'd consider making it a layered effect.
For example: When a creature first attempts to cross the threshold of the
glyph of warding without speaking the password, they experience a strange pressure in the air or vague whispering (which might also be accompanied by a subtle environmental shift associated with the spell imbued into the
glyph of warding, so a standard explosive glyph might involve a sudden flush of heat over that character's skin). Here, the DM pauses, and asks "what would you like to do?" If the PC proceeds moving through the glyph, then it triggers.
---------------------------
Inscription (magical trigger)
A magical inscription, like the glyph of warding spell, is a form of abjuration wherein runes are inscribed with glowing light that then fade to become invisible over time. A spoken password chosen by the creator of the inscription, allows a creature to safely bypass its magic.
Trap Examples: any use of glyph of warding, fire-breathing statues, sphere of annihilation
Notice: A magical inscription is almost invisible to the senses, though an Intelligence (Arcana or Investigation) check made as part of a thorough search – typically requiring at least 5 minutes – will discover barely perceptible glowing runes. If this check is made in pitch darkness it has advantage.
Detect magic will always detect a magical inscription as abjuration magic.
Disarm: Because an inscription is born of the magical word, it can be disarmed with the right password. The password chosen by the creator of the inscription must be thematically linked to the warded area/object or the effect of the spell; for example, an inscription that triggers a spell dealing cold damage might require choosing a password related to “fire” or “heat.” The details are left up to the DM and his or her campaign world.
Dispel magic cast at the appropriate level will also disarm the inscription. Finally, certain rare magical items (magical thieves' tools? magic quill?) may allow a character to subtly rewrite an inscription they are aware of with a Dexterity (Sleight of Hand) check and at least 5 minutes – on a success, the character can subtly change the password or the triggered trap at the DM’s discretion. Nonmagical thieves’ tools can’t disarm a magical inscription.
Encounter Design: It’s worthwhile to think of unique ways that characters can become aware of this trigger without
detect magic and overcome it without
dispel magic. Consider which creatures in the dungeon know the password. Additionally, when a character is initially entering an area warded by a magical inscription, the DM should give subtle clues about the presence of magic, such as an unnatural pressure in the air or a faint change in environmental conditions mirroring the type of trap about to be triggered; if the PC proceeds forward regardless, then the trap triggers.
Variations: An inscription may be reversed, its glowing writing appearing backwards to
detect magic; such a reversed inscription doesn’t trigger initially when crossed, instead becoming active a round after creatures have entered the warded area. Now, it will trigger if any creature tries to leave the warded area without speaking the password. A reversed inscription will give away subtle clues as a creature is about to cross its threshold both before and after becoming active.
[SECTION]
Age of Inscription – Level – Spell Level – Notice/Disarm DC
0-10 years – 1st-4th – 1st-2nd level – DC 15
11-100 years – 5th-10th – 3rd-5th level – DC 18
101-1,000 years – 11th-16th – 6th-8th level – DC 21
1,001+ years – 17th-20th – 9th level – DC 24[/SECTION]
