Quick background. I run a homebrew dnd 5e game with 3 friends and have been playing about 10 months now. We generally follow the rules but I generally lax them if I feel like it will make the game more fun. There was Renarto (paladin) loki (warlock) and Escanor (fighter). Renarto is a knight of the relm and is slowly being corrupted by his teammates who are a verry… moral gray party. The group got there hands on 2 magic beans they got from a treant they killed. For those who don’t know when you plant said bean you roll a d100 and there is a table that tells you what energise.
The game is set in a country where dragons are feared and hated and those who worship dragons are strung up on the city gates as a warning. This includes the god bahumat ( the platinum dragon)
Fast forward 2 months game time and about 8 months real time the party is now level 10 and all wield powerful weapons. in game the group accept the aid from 2 followers of bahmut the evil dragon god, to help the defeat a ancient white dragon that has been terrorising the mountain sides with his brood. One npc they met is a paladin of bahamut that defeated the party single handedly 4 levels ago within 3 rounds but let them live. The other (his master) a woman wearing half plate wearing a fine fur cloak and wielding a powerful sword. ( adult silver dragon in disguise). Fast forward they find the dragons lair defeat his Brood mother and then challenge him ontop of his mountain. I intended for the combat to be tough but as they would be aided by an adult silver and a high-level paldin as well as a big environmental impact that would change the battle filed providing a way for the players to either escape or potentially kill the ancient white dragon. The party fly to the top of the mountain using polymorph and scope the battlefield. There was a large ravine going down further than they could see. And the vertigo was verry unsettling. The mouth of the mountain was bridged by ice 40ft at its widest and 10 at its shortest. They went over the ice to get to the dragon. The dragon attacked them on the bridge but before it could act the paladin rolling the highest initiative ran forward and threw his magic bean to the ground. Roll a d100. He gets a 51 I look over the table. He got 51-60 — 1d4 + 8 bright pink toads crawl forth. Whenever a toad is Touched, it transforms into a Large or smaller monster of the DM’s choice. The monster remains for 1 minute, then disappears in a puff of bright pink smoke.
So I describe as the renarto throws a bean at the dragons feet and 8 pink toads emerge from the ground. The dragons steps on two of them while advancing. So here’s when I made my big mistake. I thought I would leave it mostly to the dice gods so I got the player to roll a d20 for each toad. This would be its CR. I then had him roll a d100. This was for there alignment and I would chose a monster from those parameters. He rolls the 2 d 20 and get nat 20’s!! That means 2 cr 20 monsters are about to spawn. He rolls a 18 and a 85 lower means more evil and chaotic, higher levels = lawful and good. I ignores the size parameters of the effect for the fun of what was about to happen. The dragon steps on 2 toads and a second later his foot is thrown back as an ancient brass dragon and a pit fiend both emerge as if they were in a pokeball. The pit fiend spawns 2 bearded devils. The npc silver dragon let’s go of her disguise and joins the fight at full power. The fighter is trying to deal with the devils and the warlock is just flinging eldritch blasts. The paladin who is within melee of a pit fiend and a silver dragon who he considers a hostile. The paladin runs to the next to toad and nudges them. Rolls a 9 and a 3. He spawns a owlbear and an abdominal yeti. He then runs through them taking opertunity attacks to attack the white dragon. With the rest of his movement he hits the last 2 toads. ( 2 died to breath weapon) he rolled a 12 that spawns a KI-Rin that immediately got renamed to Karen as it demanded to see the manager as soon as it spawned. The final toad he rolls a 19. He rolls and gets chaotic evil. The amount of nonsense and chaos of this battle royal that has already spawned was about to be doubled. As renarto ends his turn nudging a toad with his foot. The toad morphs in to a Balor. The balor attacks the paladin before spotting the pit fiend. He spawns 3 nalfeshnee large winged pig bear demons and now we have a fight between 2 metallic dragons and a chromatic dragon aswell as a war between a general of the abyss and one of the nine hells. It was carnage. The KI-ran used planer shift to get the f out of dodge. The owl bear and yeti got killed in cross fire. demons killed the devils, the pit fiend went on a full offensive against the balor. All the while our three adventures are freaking the f out just getting hits in where they could. The hexblade warlock deciding if its a tpk he might as well go out with a bang charges the balor. The fighter who until now has been the most chaotic player. Steps back and takes cover. The paladin charges the demons. The white dragon tries to flee when he got to 50 health and had burnt all of his legendary resistances flying away he gets chased down by the brass and killed it its fire breath the corpse falls into the mouth of the mountain. Oh and that environmental change I told you about, well that was once a corpse were sacrificed to the mountain it will erupt. I planed for it to be the npc pladin but hell why not be the BBEG!? Larva started to boil up and the bridge began to melt. The paladin was making death saves in melee range of a balor and pit fiend. The pit fiend took to the sky the brass dragon grappled the balor and the silver dragon rescued the verry bloodied paladin. The bridge collapsed and anyone still on it fell in. Only monsters none of pc’s. The paladin lost his final death save in the grip of the silver dragon. The ballor and pit fiend were finished off by the brass dragon and as he came to ask the silver What the hell happened. The 10th round hit and he vanished into a pink cloud. The players got the silver dragon to revivify there companion as he was the one in the party that was the most racist to dragons and they liked the poetry that he was saved by a dragon in the name of bahamut. We wrapped the night up and they got the 70% dragons hoard as there payment.
Needless to say that was the most insane combat I have ever had to run!