How to balance a fight with a monster who switches sides?

[msherman]

I'm planning a big battle in my game where the party starts off aligned with a (solo) monster NPC against a large group of common enemies, but then once the common enemies are dealt with, the monster will switch sides, and turn on the party.

Does anyone have any advice for how I should balance that in terms of figuring out how large the force of common enemies should be? Without the ally switching sides, it would be easy -- 5 enemies for the solo plus 5 for the party members. But then that leaves the party pretty much completely out of resources for when the ally turns on them.

Figuring the XP reward is tricky, too -- should the party get XP for the whole force? Or should I omit the ones that the ally NPC defeats?

 

[On Puget Sound]

It might be best to budget it as two encounters - party+ally vs enemies, with ally counted as a member, and then party vs allies. Add an ad hoc xp bonus for the fact that they don't get a 5 minute rest. This presumes the party has no reason to expect treachery, nor any reasonable in-game way to get warning of it.

If there was ever a moment for a character to get use out of that high passive Insight score, this would be the moment.

 

[GMforPowergamers]

In KotS (Limited spoiler...but not really)

Spoiler

there is an encounter that is done in waves, and basicly they did it as 2 encounters but ran it togather

I would count the Solo as 4 (Not 5) party members of the PC level (I assume he is 1 or 2 higher, if more maybe ad hock some more) PCs.

So it will look like this :

5 PCs 9th or 10th (a guess and just an example) level
Adult green Dragon Level 12 Solo (+4 pcs)

SO we will count as 9 10th level PCs Hard budget: 5,000 xp
Level 9 Encounter (XP 4,950)
1 orc chieftain (level 8 elite brute)
14 orc warriors (level 9 minion)
2 orc Bloodrager (Level 7 Elite Brute)
1 dire boar (level 6 brute)
2 Angel of Valor [grumpsh] (level 8 Soldier)
2 ogre skirmishers (level 8 skirmisher)
(600 xp per player)


Just 5 pcs level 10 Hard budget: 3,000 xp
Dragon 3,500 xp if it is bloodied before turning (2,000 xp)
(700 xp per player (or if bloodied first 400xp))
Make sure to spread the minnons out so one AoE doesn't wipe them, and have the Solo have an Ace up his sleave, in the example I would have Kobold minnons hiding and jump out as the dragon turns...

all and all that would be 1300 xp for (2) encounter(s)

 

[666Sinner666]

A high passive insight PC, say 20+ which is possible at level 1, should suspect, at the least, that the NPC is using them and will at some point turn on them when most opportune.

I would make the guy turn when 1 or 2 common enemies remain. That or be evil and do it when they are all dead.

 

[That One Guy]

Also, you might want to consider the moment of betrayal significant enough to be considered a milestone. This can help with allowing another action point and possibly access to another magic item use.

 

[msherman]

Thanks for all the replies. The consensus seems to be that I should just balance the number of enemies as though it were two distinct fights, in the first with the monster counted as an ally. My fear there is that the first part of the fight is very likely to suck up most of the PCs daily/encounter powers; won't that make the second fight against the solo monster much tougher than it would normally be? Or is that balanced by the fact that the monster will have used up its encounter powers (frightful presence for sure, and maybe also bloodied breath) as well?

I like the idea of counting the moment of betrayal as a milestone; if I do that, though, should I give the solo monster an action point as well?

The party is 4-6 players, and likely going to be all 2nd level by the time we get to this fight; one or two PCs might have hit 3rd. The monster is (obviously) a young white dragon. The common enemies are a goblinoid tribe -- the party already knows that there's at least one bugbear in the tribe, and a handful of hobgoblins. I haven't decided the specific mix of goblinoids for this fight yet, of course, but this thread is giving me some ideas.

Another wrinkle; the goblins are keeping kobold slaves -- that's the dragon's motivation for helping the party, she wants her cult back. Once the kobolds have been freed, I expect they'll just cower in fear and avoid taking sides in the followup fight. They're underfed and overworked, and in no shape to fight (so they're all statted as minions), and besides, there's a dragonborn in the party, so their loyalties might be split.

 

[Mahali]

You may just not have the ally spend their action point so at the mile stone you don't need to worry about it, otherwise, yes, I'd give them their AP back.

Leave the kobolds an escape route and on their action they run away. Maybe a really small crack or tunnel they have to Squeeze to move through and is too small for Medium sized creatures.

 

[Sphyre]

I ran an encounter for 4 7th level PCs that was something like this.

The beginning of the battle was a normal encounter. 3 7th level monsters and 1 9th level monster. On round 3 the monsters called in their dragon under their control: A 4th level solo black dragon. The dragon attacked the PCs for 2 rounds. Once a character hit the orb that the 9th level monster had that was controlling the dragon, the dragon was freed from control of the monsters, and attacked the monsters as well. After the monsters were dead, the young dragon was infuriated, and attacked the players who had attacked him. One of the players who spoke draconic tried to reason with him, but didn't have a very convincing story given the fact that he was saying he didn't want to hurt him, and he had attacked him just a few seconds before saying it.

Unfortunately, the level 4 solo monster was pathetic against the players. It rarely hit (more due to my dice than anything), and when it did it was low damage. I didn't want to kill the players because I designed an odd encounter, so it didn't work out that well at the end, but if I were to do the encounter over again, I would have leveled the dragon up to level 7, deleveled the next dragon up down to level 7, and it would have been much more interesting of a fight to have the dragon switch allegiances throughout the battle.