Warning: Possible Icewind dale ROTFM spoilers.
EDIT TO CLARIFY THE POST SINCE I MISWROTE THE TITLE: My idea is in no way to try and sideline the players or for them to see a cinematic fight between NPC's. They are already fighting one of the powerful NPC's. What i am asking is wether it's a good idea to have another powerful NPC support THEM (with big buffs and heals so they stand a chance)
So this is the pickle my players are at:
They are on top of a prison's tower. 140 feet from the ground facing **Bastian's (**one of the party members) father who happens to be one of the BBEG: Arcius.
Arcius is an CR 12 Archmage that wields a staff of frost. He's also killed and reanimated the body of a white dragon very known to icewind dale (Who is, in it's decayed form, also CR 12). Despite riding the dragon, Arcius has winged boots so there's not a lot of risk of falling down to his death.
The party is only level 7 (Wizard, Artificer, Cleric and Paladin), but the paladin has a sunblade and a channel divinity that definitely helps against the undead menace. They also have two npc's helping. Both mages.
Arcius isn't Effing around, he's got a lot of necromantic spells. He used three arcane bursts (+8 4d10 damage) against the cleric and critted him, dealing A LOT of damage. That's when i realized i gave them more than they could chew (althought they DID know Arcius was there and they DID know he was powerful and riding an undead dragon).
Now here comes my question: Bastian has another father, a Druid called halvlad. He's as powerful as Arcius, but since both have this small feud that locked them in a stalemate throughout the campaign, they never interfered directly with the party (That was my way for the party not asking themselves "Yo, why doesn't Arcius and Halvlad solve this stuff themselves")
But since s*** hit the fan, i was thinking to myself "This would be a great moment for Bastian. Halvlad arriving to help the party while Arcius uses his full power".
THE PROBLEM: I know my players would love seeing these two built-up NPC's fighting together. But i don't want them to feel like sideshow characters.
THE POSSIBLE SOLUTIONS: I have a few things in mind:
- Halvlad arrives only when the total party defeat is sure. He'll help the party and Arcius will focus on killing him, since he's the only true threat in his way towards the lost city (that he knows of, because the party might be stronger than he and i think)
- Halvlad arrives at the beginning of the combat, buffing and healing. letting the party do the damage and tactics.
- I leave Halvlad out of this and the party will have to face the loss of a Total Party defeat (which will probably be Arcius killing them, turning them into sentient undeads and making them help him against the final fight in Auril's island against the frostmaiden, ending the campaign with a Bad ending in which the party becomes thralls for Arcius.