D&D 5E Perception, combat, and legendary actions

[ProgBard]

A number of creatures that have legendary actions - particularly dragons - list Detect as one of the options available, described as the monster making a Wisdom (Perception) check. This has raised a number of questions for me about Perception and its role in combat.

The Detect legendary action, on the surface at least, seems a bit out of place next to the other effective things a legendary creature can do (extra attacks, supernatural effects). It's made me wonder what role making Perception checks is meant to play in combat. It's not completely obvious to me how that skill check, more than any other, is a good option in the middle of a fight - I don't see a lot of players giving up their attacks to use it, for instance. Intuitively, it doesn't seem especially ... legendary.

So - sell me on the Detect action! If you've run legendary monsters that use it, how has it given them an edge in battle? What things that PCs do does it serve to counter? And how do you adjudicate the specifics of what it does?

And while we're at it, let me know what I'm missing in general about the role of Perception in combat. Have you had it come up in a normal, non-legendary combat, and if so, what role did it play in the battle?

 

[iserith]

Good to use against PCs that are hidden. This may include invisible PCs.

 

[mellored]

It let's the creature look for the rogue, or anyone else who is trying to hide.

But mostly the rogue.

 

[Warmaster Horus]

Often only Passive Perception is available to you in combat, unless you use an action to roll a Perception check.

 

[GX.Sigma]

So - sell me on the Detect action!

Normally it takes an action. Having the option to do it as a Legendary Action means you don't have to give up your attack to do it.

What things that PCs do does it serve to counter?

Mostly the Hide action.

And how do you adjudicate the specifics of what it does?

The Rogue takes the Hide action and rolls Stealth against the dragon's Passive Perception. If successful, the Rogue is hidden from the dragon. (Write down the Rogue's stealth result.) The dragon can then use the Detect action and roll Perception against the Rogue's stealth result. If successful, the Rogue is no longer hidden.

 

[Shiroiken]

It's not going to be used often, but when the dragon knows that pesky wizard went invisible or that dratted rogue with his sharp weapon isn't where he was, it's often huge to save an Action to figure it out (especially if a breath weapon recharges).

 

[ProgBard]

Thanks for the responses, everyone. I'm getting a much clearer picture of the kind of scenarios this seems to have been intended to cover.

 

[psychophipps]

Perception makes all other actions possible...like lighting the rogue or invisible magic user on fire.