This listing looks has complete sets of monsters for Journeys in the Dark(2 sets), Altar of Despair, Well of Darkness. This would be a way to use the conversion kit without having to spend a fortune on 1E games and expansions.

www.ebay.com/itm/Descent-Journeys-in-Dark-Game-Pieces-LOT-168-Well-of-Darkness-Altar-of-Despair

Journeys in the Dark (2 complete sets of monster figs)

R 6 Beastmen
W 12 Beastmen
R 2 Giant
W 2 Giant
R 4 Razorwing
W 8 Razorwing
R 12 skeleton
W 6 skeleton
R 2 Ogre
W 4 Ogre
R 4 Hellhound
W 8 Hellhound
R 2 Manticore
W 4 Manticore
R 8 sorcerer
W 4 sorcerer
R 2 Dragon
W 2 Dragon
R 2 Naga
W 4 Naga
R 6 Bane Spider
W 12 Bane Spider
R 2 Demon
W 2 Demon

Well of Darkness (1 complete set of monster figs)

R 6 Kobold
W 12 Kobold
R 2 Ferrox
W 4 Ferrox
R 1 Golem
W 2 Golem

Altar of Despair (1 complete set of monster figs)

R 2 Blood Ape
W 4 Blood Ape
R 1 Troll
W 2 Troll
R 1 Chaos Beast
W 2 Chaos Beast
R 2 Dark Priest
W 4 Dark Priest
R 1 Deep Elf
W 2 Deep Elf