Waves of giant centipedes, with murder in their (many) eyes!

Ohh, he looks frisky! Image taken from here

Recently I've wanted to ensure that when I craft a dungeon, it actually, definitely contributes to the overall advancement to the next level/the overall advancement to level 20 (ie, a full session of D&D/a full campaign).

So I invented an encounter - actually a few but I'll describe the first for now - for a roughly third level party. Basically it's a tunnel down which pours waves of giant centipedes, their fangs dripping with fatal venom! I like to think some goblin shamans actually know spells to charm and heard the centipedes, so they become the goblins private army. The shamans like to send them out, even at long range, to potentially kill things so as to take their stuff and the killed things meat (to eat!). If things go wrong, the shamans run away down escape holes and grumbling, start rearing their next swarm of giant centipedes! Yes, the encounter respawns over time!

Actually, I'll just post a one paragraph rant on that - perhaps a respawing encounter seems screwy somehow? What seems more screwy to me is where the PC's utterly destroy say a group of monsters, but at the same time there is always another source of XP points/another group of monsters. Isn't it a little contrived? How did the first group of monsters come about? What made it? And what made the second group come about? Or the third? They just come out of thin air - which is respawning, but worse, without any nod of fictional causality and renewing process at all. I really prefer there being some boss type who set up the encounter, who sneaks away like a coward to set up another one latter. To me this is better than 'There are more monsters to slay for XP because...because shut up! There just are!'

Anyway, back to the subject. The goblin shamans send the centipedes out to kill. The centipedes get into melee on the third round, being at 160 feet, then close at 10 feet, then melee (they move fast!). Really the shamans would be better off waiting for the prey to get closer, but they kind of expect they wont and will get away, so they jump the gun. Also they think no one could hit at 160 foot range!

They come in waves, the first is a single wave. 1 giant centipede per party member.

After that the players have the option to back off and go somewhere else, or to try and press on, which will trigger...

Five waves,  one every two rounds (ie, one on the first round, one on the third round, one on the fifth round, etc). Again it's 1 giant centipede per party member.

Again the PC's could fall back, or press on to get another five waves as above.

After that, the goblin shamans forces are spent and they are sent scurrying for their lives down escape shafts too thin for them to take all their treasure with them (if they have any - flip a coin!).

The big deal is that this is 16 giant centipedes per player, at 31 XP each. 496 XP in the end, which is about 5% of what's needed for a third level fighter to get to fourth level.

And the thing is, if I were crafting rooms (like putting actual creative effort into making each room), it might take about eight rooms to have the same effect. That's putting effort in but not really getting anywhere in terms of advancement/finishing an overall campaign of this darn game I've never finished a 1-20 campaign of before. I'd like to finish one campaign at least before I die, and without pouring my heart out into a ka-billion little rooms which don't add up to much.

So that's why I invented the wave rooms! Good solid XP injection and then I don't have to worry as much that my crafted rooms aren't really advancing anything much.

But, what if the players don't attempt the wave rooms! Good question, and that's an answer for another post!