Monsters with Entertaining Features

[hymer]

In 5e, most of the iconic low-CR monsters get something that distinguishes them from the others of similar power. Goblins can run and hide, orcs can charge, hobgoblins coordinate strong attacks, kobolds gang up, etc. It all makes sense in certain ways.

The only time I've had a decidedly entertained reaction to one of these abilities, was when a goblin boss did his special reaction to put an underling between himself and an attack. That was a lot less frustrating than some of these abilities, because the PC still killed a goblin with that attack. And it spoke volumes of how goblins roll. And it is, of course, cruelly hilarious.

So what abilities have you guys tried or devised, which added more than challenge to a fight?

[Rukelnikov]

I personally love the Lair Actions 5e introduced (maybe it was 4e but I didn't play that), so I try to put them in most notable battles, even if its not a lair. For instance I DMed an encounter where there was rebellion in a town during a speech of the tyrant BBEG. Since it was a massive battle, and there was combat pretty much all over the city, I just put the tokens of the BBEG, his right hand, a couple lieutenants, and 3 or 5 minions. Each band had "lair actions", from bringing an ally from the surrounding battle to the grid so it gets turns and acts in the PC's battle, to stray arrows/spells targeting randomly.

[Wryte]

I created a set of Elite Guard generic npcs: the defender, the pikeman, the crossbowman, the medic, and the sergeant.

* Defenders have a Shield Bash attack that does no damage, but knocks their target prone, and the Protection fighting style's reaction.
* Pikemen carry pikes and can use their reaction to make an opportunity attack against anyone who enters their range.
* Crossbowmen can use a bonus action to get the attack bonus of the Archery fighting style.
* Medics have 1st level cleric spells oriented to healing and protecting.
* And Sergeants have the ability to exchange other Guards' places in the initiative order on count 20.

These guards are trained to fight in formations, with the defenders in front, pikemen in the second row, and anyone else behind. An individual guard isn't significantly tougher than a regular MM Guard - they're only CR 1/2 at most - but in proper formation they can be very tough. The defenders impose disadvantage on attacks and knock enemies prone to give the pikemen behind them advantage. The pikemen attack anyone who moves into melee with the defenders. The medic patches them up, and the sergeant keeps them in order.

[Man_Over_Game]

Have melee units that have Pack Tactics, but are wielding a large weapon with high damage and low accuracy (think Great Weapon Master feat). Combined, they force the players to plan around this, split up, or risk getting chopped up with a greatsword.

I had a pair of Goblin Champions who were twins that were psionically binded. They shared HP and had Advantage to attack any creature adjacent to the other, and could spend a Reaction to attack someone who attacked the other. Made them some kind of Twin-general amidst a small army of Goblins. Was a lot of fun.

In the end, you have to ask yourself "how will players change their tactics to deal with this?" If the answer is "absolutely nothing", then the mechanic isn't worth it and try again.

[Unoriginal]

I'm of the opinion there is not enough monsters with bardic powers.

[Bjarkmundur]

Hmmm, interesting mechanic that didn't just provide a mechanical change to the encounter.

The Dragon Fear Ability, definitely.

I gave my 4e group a lesson on dragons. I showed them how every dragon, a cross multiple editions had the Frightening Presence.
"Do you think its because dragons are scary?" I asked them.
"Yes, of course", my group answered.
"Not exactly. Dragons are so old, so powerful and ancient, it has become written in every creature's DNA to fear them. They have been on the top of the food chain for so long, that every creature in the world has evolved to tremble before them".

A few sessions later, we had travelled into a cavern in the middle of a mountain, to rescue the son of the Mayor. He was in a small cage at the end of the room, and we had yet to discover who took him. When my group saw him they ran towards the cage. The Mayor's Son hushed them, and pointed behind them.
You should have seen my players ACTUALLY PHYSICALLY SHUSH EACH OTHER AND START TO WHISPER when they saw the sleeping dragon lying on a treasure hoard, under 50 feet away from them.

The dragon never woke up, but the suspense was higher than in any combat encounter I have ever run.

And here's an arbitrary story of how mechanical effects actually can drastically change how an encounter plays out.
In 4e I had my most powerful bosses have some kind of adamaging Aura. This was necessary to challenge the total HP pool of my players. Once my player started to expect this, I could play around with it.

I changed the Aura to a "donut", so if you were adjacent to the boss, you took no damage from the Aura. It was really fun watching all the ranged characters run around as my boss teleported. The boss then had two tactics. She started the fight by using the Aura to force all the players into melee, and continued to kick their ass from there. Once my player realised she was strong in melee they tried being avoiding the Aura and her melee attacks. After she got bloodied her focus changed to "use Aura to force them to get them into melee" into "use the Aura to kill them, since I'm dying and don't want anyone slashing me with a sword."