I am currently playing Boulders gate : decent into avernus as my first campaign. IT IS AWSOME. We have been playing from the start of the year and we are about halfway done, we are lvl 7, the party consists by our human forge cleric/fighter, a dwarf wizard (I am not sure about subclass) , a tiefling fiend warlock, me a high elf assasian rogue and the hero of this story Agis our half elf rune fighter. We were driving in our tormentor(a war machine with about 100 HP) and going to negotiate/fight with a dragon God(crazy staff) , but since the journey was too long and we had some extra time irl our dm made for us a random encounter. Now keep in mind that this dude is an awsome dm but whenever he made an encounter it was kind of a pushover, usually a high cr monster but always alone and we knew it was coming waaaay before it could attack so casualties were rare(I was the most common person to go down due to my character being 110 years barely adoult by elf standars), the point is his fights were usaly easy.
So when 3 motorcycles came in our way we all thought yep this is gonna be easy. So the fight begans, one of them dies due to hitting a rock but the other 2 devils hop into our car our cleric Sparta kicks one of the down and then we find out that another tormentor who carried 4 devils(witch al of them were the same race as a BOSS that we had previously faced) and a deamon grinder (the most powerful war machine) were right in our tails (we saw them since they crushed the kicked deamon becouse they were in a cloud of dust). WUT? Well dm had learned his lesson.
After a brief fight our viacle was destroyed and every single one of us was knocked to the ground exept our cleric who had jumped into the deamon grinder. Untill the enemy viacles could reach us (because they were at full speed and needed to come all the way back for us, we finished the last 2 devils that were on our tormentor and then Agis had an idea. He activated his rune that made him a large creature (I believe) and ask from our wizard to cast a spell to double his size, in the end he was even Bigger than the enemy tormentor(not sure if it was allowed or our dm just rolled with it because it was so epic but whatever). He braced himself and the tormentor (failing a dex save) crushed into him for 10d10 dmg to both (wich turned out to be around 35). Then with the viacle being weakened in the following turn he CAUGHT IT IN HALF.
The rest of the fight was easy with our warlock blasting from a distance, our cleric and his spirit guardians killing the devils in the deamon grinder, me helping him a bit and harpooning a devil that was after our wizard and our wizard casting FIREBALL3 TIMES, jk, jk, summon minor elementals for 4 ice elementals (can’t remember the name) to fight the 4 devils that were like the dungeon boss we had faced. In the end we got 3 devil real names(so they become our bitches for one time when we call them) , a new car ( the deamon grinder) and an epic memory. Not to bad for a randome encounter right?