My campaign calls for characters of a certain level for the final boss fight. How do I best get them there?

Question

In a custom 5e campaign I've designed, the big boss is a very powerful entity. It is not stylistically reasonable for the players to fight it below level 17. They are currently level 6. My planned campaign content should take roughly twelve (12) 4-hour sessions to complete. This means, in order to reach the desired character level, the PCs must gain one level per session.

As for why the final boss fight should be a very high-level encounter,

the Big Baddie is an ancient spellcaster of immense power. Changing this is difficult, as in our already-played sessions I've baited the players with high-level abilities, such as demiplane creation and travel.

Leveling up once per session seems unreasonably fast. I worry the players won't have time to adjust to new abilities and spells, but also that it will be difficult to convey that reaching such a high level was an achievement. In addition, the experience required to do this is very high; employing the milestone method seems to cheapen the difficulty of reaching such a pinnacle of power, but actually earning the required experience will require every encounter be of Deadly level or higher.

Possible solutions I've come up with:

• Add more content. I can certainly develop more content, adding more sessions to the campaign. This would seem an obvious solution, except we typically play 1-2 times a month. 12 sessions will take at least 6 months, more likely 9 months. I am loath to extend this by 8 sessions (to a total of 20), which would be the rough minimum to make it not feel like a level every session.
• Change the big boss. I can make the boss different, scaling difficulty down and enabling the final encounter to be less than a level 17 fight. This would be fairly simple mechanically, but require massive changes to the plot- some of which would be difficult to pull off, since we are already three sessions into the campaign.
• Increase the leveling speed to match, as discussed above.
• Find a story reason to give more experience than granted in sessions. "You spend a week fighting bandits and get 12000 experience" would be a (terrible) example of this principle. If done well, with random event tables the players roll against and fun "scripted" events, this could allow the fast leveling required without constant near-death fighting in every single session, but still suffers from possible problems resulting from such rapid advancement.
• Something else, perhaps?

How do I best get the PCs from level 6 to 17+?

---

Following advice from SevenSidedDie, I'm posting the real question. We'll see if it works or if it needs to be adjusted/edited/asked differently.

Answer 1

I would recommend doing the following changes.

1. Expect the characters to reach level 12.
2. Give the characters very powerful magic items.
3. Reduce the CR 17 big bad to a CR 15 big bad. If the big bad needs to be level 17 to have access to a spell, ability, or collection of spells, then give the big bad an item which replicates that spell. (For example, perhaps the power comes from the building they occupy, combined with some artefact, rather than their own skill) Alternatively, you can reduce the CR by giving damage vulnerability, or fewer HP.

This should allow them to level up over 2 or 3 sessions, and give enough fights between levels to feel the achievement. The extra magic items will allow the big bad to be a challenge but beatable and you won't have to adjust your planned content too much. My advice is partially based on the fact that the published adventure themselves don't actually take characters to level 20.

Answer 2

In Hoard of the Dragon Queen, the option is given to simply award levels at certain milestones in the story rather than tracking XP. In addition, you could combine both options for even faster advancement. This has worked just fine in my experience but with one caveat: if players level up too quickly they will often not get used to their new abilities enough to use them effectively.

When I want fast advancement I usually have players grow between 1 and 2 levels per session, depending on the length of the session and difficulty of the adventure. If you do this, you have to take into account this fast leveling when designing your adventure. I have found that you need at least two interesting battles at minimum between levels. On the first, they can learn and show off their new powers, they have a chance to make mistakes. The second one is tougher, it often includes traps or smarter enemies.

Answer 3

I've encountered this issue before in some of my own campaigns and I've come up with some of my own ways to cope with it. Here is what I've used:

1: Side quests! If the players aren't ready to take on the big baddie, find a reason to send them on a side quest. This gives the players a break from the main campaign, and gives them a chance to gain extra experience, magic items, and whatever else is needed.

2: Give the group an overpowered NPC in disguise. I had a campaign where the group came across what appeared to be a friendly cat, which was quickly adopted by the group. The cat turned out the be a gold dragon who had taken interest in the group. It wasn't revealed until the group faced an encounter they clearly couldn't survive, when suddenly the cat turned into it's true form and defended the group. There are some issues with this solution; obviously it takes a lot away from the players, but if you have a good group they'll enjoy the surprise and just be happy to have survived the encounter.

3: Magic items! Not only can players find powerful magic items which will help the group take on enemies that are more powerful then the character, but there are also some magic items which just increase the level of the user. (I haven't played 5th edition, so I don't know if it's called the same thing, but in 1st edition there are items called ioun stones. One stone specifically, permanently increases the user's level by 1).

3A: Along the same lines of magic items, what if the players find a special magic item that's sole purpose is to weaken the big baddie? This could be another side quest or a part of the main quest.

4: Weaken the big baddie: Ok, maybe it HAS to be the power level it is. But maybe it's sick, or asleep when the players show up. So, either it isn't able to fully wield the powers it has, or the players will get a chance to do some serious damage before the enemy gets a chance to retaliate.

5: Give the players expendable NPC's: Say the players know they aren't a match for the big baddie alone, but maybe with a small army they might be able to handle it. Have the players recruit some low level NPC's to be used as meat shields. During the fight have your big baddie mostly target the expendable NPC's to give the players more of a chance.