I tried something new for this week's session. The players were going to be fighting an Earth Kraken, which is my CR21 take on a kraken, but tunneling.
This thing was super-duper fun because I changed up the legendary creature formula. Here's what happened
I made a legendary monster that does this->
Initiative 18: Earth Kraken's turn. It bursts from the ground. All creatures within 10ft of it must DEX 20 save or take 4d10 piercing damage from flying rock shards.
At the end of it's turn, it launches itself into the air towards a point.
Initiative 10: The Earth Kraken travels half the distance towards it's chosen impact point.
Initiative 0 : The EK crashes into the ground and tunnels down. The shockwave deals 4d10 bludgeoning in a 10ft radius, DEX save 20 to avoid. The earth sinks, miring all creatures up to their waists (prone).
Note: It was a 55ft creature, so including a 10ft radius from the edge of 55ft critter is a BIG total area. That's why it's only 10ft.
Also note that it's underground for a small but useful part of the initiative cycle.
The red rectangle is a giant area of DO NOT STAND HERE. Good times!
Anyway, the Earth Kraken erupts under the players' feet for damage, maybe bite+swallows a target, maybe grabs people with its tentacles, and then launches through the air.
It travels during the round and then crashes like a bomb which also reduces escape chances for next round.
This was a wild good time. The players quickly realized how dangerous this was and they all bailed into a demiplane mid-battle. They regrouped and baited the creature into eating an immovable rod, which shut off it's primary damage pattern. It was brilliant.
We still had a fierce battle from there since the Earth Kraken's tentacles could reach into the demiplane. They'd cracked the door open so it breached their bunker. It was 20,000 Leagues Under the Sea from there ^_^
Lots of fire. Lots of hacking. Then, when it had no more tentacles...
The Earth Kraken put is giant mouth over the door to the demiplane and tried to suck all the players into it's mouth. Mwahaha.
I only got the warlock with this one, but he was facing 12d6 acid damage/rnd now and that really made the rest of the party put the petal to the metal for the finish.
Some design notes
I wanted a creature that had broadcasted abilities rather than legendary actions; which just go off. This allowed the players to cast, scramble around, and strategize about how to survive.
I also made the saving throws all or nothing, rather than half damage since it still has it’s normal turn’s worth of attacks and a 30ft tentacle reach. It does plenty of damage-per-turn already. The secret to a good situation in-game is for it to not end too quickly. If this was swinging 100+ dpt then it wouldn’t be a long fight. (Rather, 100+ dpt versus a level 18 party who lacks a full healer.)
Overall
This was a really fun fight that we all enjoyed. From here, I'm considering changing up legendary actions for future boss monsters. The legendary action will be announced at the start of the active player's turn and go off at their end.
I think doing that would inject more player agency into the legendary action equation and make boss fights feel more interactive.
I'll need to retool some things though. Not sure about the specifics. It depends on what they fight next.