D&D 5E I need some "Watchdog" Monsters

[shadowoflameth]

If you are willing to convert a creature to 5E, back in 4e was the Gremlin. There was one that became invisible when an enemy was adjacent to it. I had the as guards once and the rogue snuck up on them. Whoops.

 

[Stalker0]

But... you're the DM.

Pick any monster. Give it profiency in perception. Expertise even. It's been specially bred (or recieved the appropriate training).

Always an option of course, but its nice to know what the raw material is before I start messing with the clay.

 

[Flamestrike]

Always an option of course, but its nice to know what the raw material is before I start messing with the clay.

I'd just pick a monster, give it proficiency in perception (ore expertise if needed) and then a trait 'cannot be surprised'.

It'll work for pretty much anything.

 

[aco175]

Are you trying to prevent the PCs from sneaking past or getting in, or trying to make things hard and challenging? You could have 10 dogs and handlers being led around in 1 minute circles or you can have 1 dog with 2 guards standing over there.

 

[Quickleaf]

Winter Wolf has passive perception 20 (including Keen Hearing and Smell).

 

[The Grassy Gnoll]

Good old fashioned AD&D style Magic Mouths all over the shop, triggering alarms in an ascending shrillness that even Dh’orisz - the minimum waged, half-blind, geriatric kobold that they keep on the payroll out of pity because she’s been there since Rossothrax was a hatchling - even she can shuffle over to the boss’ door and give them the heads up with plenty of time to spare.

 

[Eltab]

A galeb duhr (sp?) can just sit and wait forever for something to show up, effectively able to Take 20 on its Perception roll.
The PCs see -whatever it is guarding- and three big ornamental rocks out in front.