How do I make encounters with massive creatures fun?

How do I make encounters with massive creatures fun?
I'm playing 5e and my players have built up some lore (they like to improvise) regarding a massive monster, so I intend to make it plot relevant in the next session.
However, I am conflicted about how to make the encounter, as "hit the big monster until it's dead" is pretty boring. How do I make the encounter fun for my party without being a slogfest?

Since the creature is a laboratory experiment, I was thinking about it being controlled by a number of mages & rune totems. It will attack with large, damaging area of affect abilities, which are dodgable, but just enough to instill some danger to the players. If enough of the mages are distracted/rune totems are destroyed, the beast will go berserk against its captors, ending the encounter as it breaks free and heads into the sea as the BBEG curses them and teleports away.
Does this sound exciting, at least? Combat that drags on and doesn't require any form of creativity bores my players

Either that or take a cue from video games and have some weakpoints on it you need to target. Hell, make the monster the arena, have the players attacking like "pimples of power" or something on it's back while they're getting attacked by tentacles, parasites and have to make saves to avoid getting shaken off.

The encounter you described sounds fun. Another idea would be to get inspiration from Shadow of the Colossus. Have the PC's need to mount and attack certain weak sections of the beast to take it off it's feet before trying to deal a death blow.

>goes into the sea and escapes
>presumably to do whatever giant sea monsters do

Make it a twist that it remembers your group as the ones who set it free and it comes out to one shot a potentially game ending enemy and eating it.

You can also use its own attacks to break the rune totems because they're aoe attacks

>as the BBEG curses them and teleports away.
>TELEPORTS AWAY

You are the cancer.

Then how can I physically introduce the BBEG in person without my players instantaneously charging him or just producing a wall

> my villains sit around like xp piñatas

No u

There's a million ways.

My first instinct is usually to make him ridiculously powerful for my players level. Dodges any attack that requires an attack roll like Cyborg Batman, tanks anything that doesn't require a roll with a laugh, etc. then just gets bored and dares them to follow, dropping ever harder encounters in their path if they do.

This also throws up possible side quests where they learn the secrets to his powers and can quest to overcome them by finding ancient artifacts or the like.

tl;dr: BE CREATIVE, DUM DUM

>Not coming up with helpful alternatives and just criticising
Mhm, they're the cancer. Sure.

Depends how big you're talking.
Dragon-size creatures need to be able to have some mobility to them, we're talking flying, swimming, giant leaps, anything to stop the combat turning into a slog and keep it moving.
It needs special attacks, something for the players to fear (think dragon breath) but it needs something that can be played around (like not clumping up)
Maybe think about some specific weaknesses, ways they can drive the monster to its knees, or force it into a lava pit and so on.

My players are particularly bullheaded and would probably keep trying
But I see what you're getting at, I'll try getting some ideas
Maybe he'll come in and the creature will attack at him, be punished by the BBEG, and the creature will use that opportunity to break one of the last binding totems, so the BBEG will retreat before suffering the full weight of the unleashed creature

Read
The
Monster
Manual

Add in some Legendary effects, both for the lair and the monster. Every round they should have to deal with the monster, with the things in the lab either exploding or reacting to the monster ,and the effects of the wizards doing things to it. It should get a few free actions to keep things from getting stale.

I have always liked using AOE's and broadcasting huge hitboxes and stuff with bosses in my games, but a lot of people think that's way too 'videogamey.' Just make sure that your players aren't just standing in front of the beast, who isn't moving and it turns into a full attack fest. The combat should be dynamic, standing in front of it should be stupid and bad, to encourage things like getting up on the monster's back or attacking from a distance with labatory super-science guns

You could make it so the rune totems are scattered in the ventilation system beneath the room where the big creature is
Tiny thieves and the like have to crawl around down there and disable traps/destroy the totems while the rest of the party on the main floor has to distract the big monster so that the character in the vents isn't hit by the aoe of the monster's earthquake attacks

Example:

My party tried to chase a particularly nasty bad guy, later to turn out to be just a lieutenant, and he eventually got annoyed by them just catching up to him over and over, so he tossed a little silvery-red egg on the ground between them.

The egg hatched and a little red lizard came out. Sensing the bad my party fired some magic at it. It absorbed each blast and increased a size category every few hits until it was a red dragon just large enough to challenge the group for a few minutes while their target got out of sight. It would have also grown into the same dragon over a longer period if they had ignored it.

My players had mad tracking skills, but after a day of following the trail it just ended. Magical analysis of the trails end gave them a clue as to where the guy went, and hooked them deeper into the plot

On the giant monster bit: Why not have it controlled by a series of people/smaller monsters spread across the town/countryside? Each could be tough enough to challenge the party a bit, creating a running fight/search to find all of them. Also, hitting them hard enough could make them break concentration for a second, allowing the beast to lash out at its oppressors or the like.

Also... Apologies for the dum dum part. My coffee maker shit the bed this morning and I'm in a bit of a mood.

I had a GM try an expirement with a giant so big it's limbs were their own enemies. (An Exodia kind of deal) A huge left/right arm/leg, and the mainbody with the head.

Award the use of creative tactics. If someone figures out a way to trip it have it take a ton of damage, stuff like that.

>On the giant monster bit: Why not have it controlled by a series of people/smaller monsters spread across the town/countryside?
Oh woah that's cool
You could turn it into a little sleuthing exercise where you have to uncover the secret cultists and scientists who are posing as simple farmers and then handle them simultaneously

The design pf AT-ATs annoys me unnecessarily. So structurally unstable.

Shadow of the Colossus.
Climb it, hit it in the eye, tear bits off, etc.

Or they encounter it at a level far below it's CR, and have to overcome the challenge in other ways. Like fighting godzilla, you have to lure it into traps, or seal it away for a thousand years. Or at least when you're higher level.

And/or they could be revealed by glowyness or something during the attack and it's a mad dash to get them before the town is totally shithoused by the giant monster.

>monster shows up when the party is preparing to attack the BBEG's fortress
>gives a little growl of acknowledgement, then begins smashing a path through the defenses

>your bad guy lieutenant just abandoned his Pokémon

He'll never beat the Elite Four that way.

Hell, the 5e DMG even has an optional rule for climbing onto bigger creatures.

I feel like once a creature gets big enough you need to treat it less like a creature and more like an environment.

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