Advice for increasing the difficulty of an encounter

[Zahariel]

I'm running my group through the Academy of Secrets module, sort of stretching the old GM muscles before tackling Jade Regent, and I've come across this situation:

They're breezing through it. It's no challenge whatsoever.

(Also, guys, if you're reading this, no cheating!)

The problems so far::

The level of optimization and synergy of the party is uncanny. Which is good, they're playing together, but to the point that no encounter as written comes even close to challenging them. The party is made of a monk, a wizard, an alchemist, a barbarian and a paladin. The only encounters they have left in Belzeragna are Marijkal, the Dueling Arena and Chyvom, and I would like Chyvom at least to be able to present something of a challenge.

The whip-wielding paladin deals no damage as he's taken a variant that instead gives a massive bonus to CMB to trip, but the barbarian dishes 50+ damage each turn, 98 when he maximizes his dice. The monk is a really well built damage dealer that also stuns, and the wizard specializes in ranged touch attacks with devastating efficiency. The ragechemist alchemist rounds off the party with potions and additional damage.

When it comes to Chyvom, I want to be able to RP the encounter. For a while at least. The group is no enemy to a good rp, but my concern is that if it comes to combat, the Paladin is bound to win initiative, trip Chyvom and he won't even be able to write down the licence plate number. So on one hand, if he's alone, they are going to massacre him as soon as the conversation ends. But if he's not alone, they will take that as a threat and rightfully charge into battle, and most likely win in a couple of rounds. The wizard has only used two spells so far, none of them over level 5 and they haven't needed any healing so far (they offed the bone devil in the Lecture Hall in one turn and the barbarian put Illia Ean in 3 hit points with a single blow).

Any suggestions? I'll admit I'm clueless.

[Weables]

I haven't run the module specifically, but I can give general advice.

A party of 5 can be considered APL+1 if they're decently optimized. APL+2 if they are amazingly optimized as a team. This means you want to up encounters. I dont know what level you are, but sounds to be 8-10 if the barb does that kind of damage. If it's lower, you want to take a look at his sheet and check for shenanigans, since thats about right for a well optimized barb at those levels.

Information like point buy, level, builds, feats, etc would help.

Other general tips: Single big bad monsters are weak for their CR, they lose the action economy fight. throwing lots of mooks in (dwarves if it fits for stability, things with extra legs to slow the paladin some) helps add challenge while the big bad can be a lil safer and do some damage.

[Talon Moonwalker]

Preperation, spells, and summonable minions are a good idea if only to slow the party down. Add templates to monsters and so on to give them bonuses.

Remember, if you stat it, it can die. Just ignore HP for a while till they have a decent fight, and then actually let the guy die. Remember, the rules are guidelines, if something doesn't work for you then change it. You can safely add a lot of HP because of the 5th player present, and if they are as optimised as you say they are, then give the monster more class levels. A decent party can blow through the CR system and punch far far above their weight. I learnt this the hard way

[Avenger]

Add the Advanced teamplate to monsters.

[Zahariel]

The encounter I need to up the CR for is an [already advanced] contract devil that waits for the characters to enter his office, and in a very Mephistophelean way, offers them a deal for their heart's desire in exchange for future services, and if they don't accept the offer begrudgingly starts the fight by summoning other devils to fight them.

The problem is that there are two characters, the paladin and the monk, specialized and optimized for combat manouvers. The contract devil has a CMD of 43 and from previous encounters they are hitting 55+ on trip and stun rolls. If they win initiative, the fight is over, as the rest of the party can easily dish 200+ damage in a single turn.

I'm trying to find a way to increase the difficulty without robbing the BBEG of his calm and collected self-assurance during the dealing-with-the-devil stage.

[pipedreamsam]

Play the Enemies like they are super genius expecting a party of adventurers to try and ruin their plans. Nothing says calm and assured like I knew you were coming and I know all of your weaknesses and I prepared accordingly, "Your move, future property."

[Zahariel]

Thank you. I think I may have thought of the way to do it.

[Mergy]

He's a devil? Does he, by chance, have wings? If he's hovering, no trip.

If you're okay with adding things you could put in some magical wards/traps set up in his office because he's expecting things to throw down, and can offset their first round of bang. Even just something that would force reflex or stop/fall down, or will save or stop would be enough to let him get in a good round of stuffs.