How does crown of madness work when triggered using glyph of warding?

Question

Let's say that:

1. I cast Glyph of Warding and imbue Crown of Madness into it, with the trigger being a creature in a party of 2 or greater steps on the glyph.

2. A party of 2 walks over the glyph and the first creature triggers the glyph.

3. The creature fails his Wisdom saving throw.

4. I, the caster, am nowhere near the glyph, meaning I have no sight of the creatures and no way to know the glyph has been triggered.

   A. Can I still mentally choose a target for the creature to attack?

   B. Can I make him attack his buddy?

Answer 1

One way or another, crown of madness is not going to work. Either:

1. When the spell says "you", it means the glyph of warding, in which case crown of madness will work, but you won't be able to choose a target, so the victim will be able to act normally.
2. When the spell says "you", it means you, the caster, in which case, you can't see the target, so crown of madness won't work at all.
3. When the spell says "you", it means the glyph of warding, and glyph of warding is capable of mentally choosing targets, in which case crown of madness will work, but glyph of warding will always target the creature who triggered the glyph, and crown of madness doesn't allow you to command a creature to attack itself.

Answer 2

Crown of Madness will work, it just won't work well.

... make a melee attack against a creature other than itself that you mentally choose. The target can act normally on its turn if you choose no creature or if none are within its reach.

A kind DM may allow you to mentally choose "the nearest companion", if so, no problems; an unkind DM may decide that you cannot choose therefore the "target can act normally".

Either way, it probably only works for 1 round:

On your subsequent turns, you must use your action to maintain control over the target, or the spell ends.

Again, a kind DM may allow you (wherever you are and whenever this is) to use your action to do this - after a spell is cast range is not an object. Unless you are asleep, or dead.

Answer 3

How it should work:

The glyph chooses the target, which is the valid target that it thinks will result in the most harm to the spell's original target. It's not intelligent, so that should just be the creature with the most hitpoints, probably. This is consistent with the extant spell text's clear theme that the spells function in such a way as to be bad for the target with no concern for anything else.

How it does work:

Yup, you choose whatever target you want and the creature must attack that target. You don't need to be able to see the target, because you aren't casting a spell and the spell doesn't say you do, but the target must be within reach. You don't automatically know that the glyph has triggered, and you don't get any information regarding potential targets or the lack thereof so-- without some sort of additional defences and assuming you don't constantly mentally choose a certain target as an off-turn free action during every turn all the time-- you'll not choose any target and the affected creature will act normally, despite the sudden iron crown and mad gleam in its eyes.

Answer 4

Glyph of warding allows you to cast spells that require consecration without needing to concentrate on them, so long as they do harm.

From my understanding, if properly worded, crown of madness will work.

This glyph of warding would be worded to trigger when at least two creatures come within range, it casts crown of madness on the second creature to enter is range and forces him to attack the first creature that entered range.

As the caster, the glyph of warding gets to use crown of madness as written. However the glyph of warding is not sentient and so cannot choose to make a creature attack another creature unless it was instructed to when it was cast.