D&D 5E I need help to create encounters for a mountain climb

[Quickleaf]

They have very much the chance to not find the gate, and if they do find it they are probably in bigger trouble since inside the gate there is a Fire Giant and his Hell hounds guarding a entrance to the Underdark, if they manage to convince the Fire Giant that they are trustworthy they gain a strong ally but if not there will be one hell of a fight, besides that my players are super curious and will probaly try to go to the Underdark even if they are a bit underlevel to go there in my eyes

Gotcha. So it sounds like the stakes during the mountain climb are: Will they find the golden gate?

In that case, think of the mountain climb session as being all about the search. They know it's somewhere on the mountain, but not exactly where. So they're hunting different areas of this mountain, searching for clues which point to the golden gate.

You can see a skill challenge I put together for a similar concept (searching a jungle wasteland for a bone palace) over here: [5e] Help with a travel skill challenge? Most of the work went into designing a sort of logic puzzle which the clues helped guide the PCs toward solving; so it was a process of elimination – "Ok, it's not hexes A, B, C, D, G, or H based on this clue, and this other clue tells us it's not hexes K, M, or N, so we know..."

 

[Jv_Stuchi]

Gotcha. So it sounds like the stakes during the mountain climb are: Will they find the golden gate?

In that case, think of the mountain climb session as being all about the search. They know it's somewhere on the mountain, but not exactly where. So they're hunting different areas of this mountain, searching for clues which point to the golden gate.

You can see a skill challenge I put together for a similar concept (searching a jungle wasteland for a bone palace) over here: [5e] Help with a travel skill challenge? Most of the work went into designing a sort of logic puzzle which the clues helped guide the PCs toward solving; so it was a process of elimination – "Ok, it's not hexes A, B, C, D, G, or H based on this clue, and this other clue tells us it's not hexes K, M, or N, so we know..."

Cool, i will take a look and come up with good clues to the gate location

 

[NotAYakk]

The mountain is the first problem.

When you are on the mountain (past the base) you cannot long rest. The air is too thin. Short rests take 8 hours. And above a certain line, there is no more short rests; every hour you simply get a level of exhaustion.

Second: Everything is a dungeon!

3 starting paths, each with a fork into 3 sub paths. Those 3 choices can overlap.

A1
A2
A3 = B1
B2
B3 = C1
C2
C3

Now populate them; in general roll 1d8, rerolling duplicates. 1 is the path to the gate (on an 8, it is via path D). 1 tells you about route D (see below). 1 tells you about the guardian of the gate. 2 give clues asto which is the right path (eliminating some paths)

D is a path you can only find via the above hint. D3 is either a treasure, or the gate, depending on the result of the d8 earlier. One of D1/D2 is the gate if D3 isn't. Ones that aren't the gate, roll 1d8 skipping the gate and the clue where path D is.

This gives (A,B,C)+8 = 11 nodes. Each node should be populated with a challenge; a short rest's worth of encounters (either one hard-deadly, or multiple weaker ones) or something else.

Possible labels for A B C:

A: Climb the Glacier
B: A Goblin-spoor path
C: Up the River-Canyon
D: Underdark/Tunnels

Foes:
(A) obviously arctic monsters. Cracks in the ice. Blizzards.
(B) obviously goblins/humanoids. Harpies.
(C) obviously water creatures. Storm giants playing with lightning bolts.
(D) goblins or other underdark deziens. Lava and monsters. Fungus (from underdweller farms)

There. Lots of choices, and they aren't false. Dead ends to explore. Retreating down the mountain in the face of environmental difficulty.

That is 10 encounter-bundles ("scenes").

Now, 6 level 5 characters have an encounter level of (6*4)/4 = 6+1 = 7. Harpies are CR 1 with an encounter level of 1 per Harpy.

Your per-scene budget is 10 (4/3 encounter level of party) and your per-encounter discount is 2 (1/3 of encounter level of party).

So they are on a 40' level area, and 4 harpies attack, trying to lure them off the cliff (+50% difficulty due to terrain). Defeating them, they can go after the nest of 8 more harpies (but no longer as likely to go over a cliff) to secure the location. Note that song immunity is per harpy; they'll have to accumulate 4 successful saves in the first fight to not be lured off the cliff (!). DC is only 11, and you get 1 save initially, 1 at the end of first turn as you walk to the edge of the cliff, and 1 save the next turn or you plummet off the cliff.