My favorite extra monster book is the 1e Fiend Folio. Open it to just about any page. Odds are very high that I've used the critter more than once.
Several particular favorites (that aren't Drow) are:
*Osquips
*Death Dogs
**Hook Horrors
**Grell
*Crypt Thing
*Oriental Dragons
But the list just goes on & on & on.
One very memorable adventure was with Bullywugs + a Pan-Lung Dragon.
It all started out as a purely randomly rolled encounter as we were playing the Saltmarsh series. The players had completed Danger at Dunwater (and not
totally botched it up
), thus learning of the Sahuagin threat to the area. So they'd reported back to Saltmarsh, rested, re-equipped, leveled up, etc. & the town council sent them back out to scout this new threat. They
could've taken a boat down the coast. They decided to make the journey on foot though so the the Sea Devils wouldn't see them coming. Wich meant they passed through the Hool Marshes.
All along the way I'm dutifully making the random encounter checks as prescribed in the module - and nothing of any real interest or note is occurring. One of the non-interesting encounters rolled was with a # of Bullywugs. Things were pretty dull so I had the frogmen ambush the PCs - even though this was, at best, only mildly challenging for the group. To no ones surprise they repelled the ambush & banked some xp.
Eventually they get to the Sahuagin lair, scout it a bit, determine there's a sizable threat present, & withdraw in order to plan.
It was at this point that one of the players suggests they
go seek out the aid of the Bullywug King!
(I, the DM, thinking: "Um, what Bullywug King?? Those were like six random dudes that attacked you.... And why in the world do you think Bullywugs would want to help you??)
My response? "Uh, OK...."
And so the party set out searching the Hool Marshes for the Bullywug King....
The rest of the evening was spent exploring miles & miles of D&D Everglades, dealing with random swamp encounters, & hoping to run into more Bullywugs -
to talk with.
I had no plan for how this would go. I figured that eventually one of two things would happen: A) The session would end & I'd go home and write something up proper for next week, B) Bullywugs would be rolled up again, they'd be the lead to their "king", & I'd end things for the week with the PCs approaching a Bullywug lair.
No more bullywugs were rolled up. BUT, towards the end of the session I did roll up a Pan-Lung. WT* is a Pan-Lung?? Looks in the FF - "Oh, a Chinees(?) water dragon." Second thought upon reading it - "MY GOD! That's nowhere near what these characters could handle. WHY is this thing on this random chart??"
So I had them encounter it polymorphed into human(?) form as a non-combat encounter. She gave the PCs the location of the Bullywugs they sought. She also warned the PCs that Bullywugs are vicious evil creatures that shouldn't be trusted....
End of session.
I then went home & wrote some stuff up.
*The Bullywugs would help the PCs by committing 50 warriors IF:
*The PCs rid them of an evil Pan-Lung that had taken up residence in their territory & was killing them off. It's lair was in the ruins of a sunken temple complex sacred to the tribe. Directions provided. Return with proof.
The PCs readily agreed to these terms. Though they never once asked
what exactly a Pan-Lung was. And I know none of the players knew.
So the next several sessions were spent delving a sunken ruin (using the Xax-Tsaroth maps from DL), fighting the Pan-Lungs Xvart minions - who appeared to be rebuilding the place, & having great fun. Eventually they came to the attention of the dragon herself.... (she came home to find work disrupted, her minions being killed, and her stuff being looted) The players were surprised to find out it was the woman they'd met the previous week. They had no idea she was a shapeshifted dragon, but talking to her they
were aware that all was not as it seemed.... and she readily admitted to having driven the Bullywugs out of this temple and killing any who dared return.
They were just entering negotiations when the parties barbarian declared that no deals would be made with the evil Pan-Lung who was oppressing the Bullywugs & attacked.
The players learned what a Pan-Lung was as she dropped the disguise & ate the barbarian.
Negotiations resumed.
And again the party did the unexpected. They'd just met a dragon who had no qualms about wiping out Bullywugs & eating barbarians. You would think this would be a great ally to recruit vs the Sahuagin.
Instead they worked out a deal to take false proof of success to the Bullywugs to secure the 50 warriors deal.
And again they were warned that Bullywugs are vicious evil creatures & NOT to be trusted.
About 1/2 way back to the Sahugin lair? The Bullywugs carried out Order 66 vs the party.
The ONLY reason this was not a TPK was because rather than run 50 Bullywugs myself in combat I gave the Barbarians player control of half of them. Rolling in the open, the only thing he managed to kill was a single wolf belonging to one of the PCs. Yes, his dice rolls really were that awful. I witnessed it. The PCs ended up killing just over 1/2 the attackers & broke the frog guys morale. (I mean, when you have the prey outnumbered 10-1 {counting their dog!} and half your force gets killed....)
*The Barbarian player, outraged that it was possible to encounter a Pan-Lung at this lv, dropped out of the game.
*The remaining PCs went on to deal with Module U3 without Bullywug or Dragon support.
*The surviving bullywugs reported back to their king that the adventurers had been killed, eaten, & had been delicious. And hoping that the PCs wouldn't return.
**In a later campaign it was learned that the Bullywugs, believing the PCs had dealt with the Pan-Lung, had returned to the sunken temple. They were quite surprised by a very much alive PL & quickly killed.
All of this stemmed from two rolls on a random encounter chart in a classic 1e module & used creatures out of one of my favorite 1e books.