Has there ever been a list on the catalogue of morphs gathered by Visser Three?!
Not that I know of. How about we start one?
This is from memory, there are a bunch of gaps:
Book 1: Antarean Bogg morph: Two legs, two tentacles, big mouth, eats Elfangor
Yeerk Pool morph: Eight heads, eight legs, tree trunk body, shoots fireballs
Book 2: Yeerkbane Varnarx: Used through hologram to intimidate Chapman
Rock monster, possibly a Jubba-Jubba from the Hork-Bajir world?
Book 11: Lerdethak: Monster with a bunch of vine-like tentacles from the Hork-Bajir world, defeats the Animorphs in the jungle
Book 15: Big yellow sea snake, used while Animorphs are at Visser One's underwater base
Book 17: Pterodactyl-like bird morph used in Yeerk Pool
Book 20: Dule Fansa, used in David's house, Barney with a bunch of pile-driver missiles
Book 23: Aria
Kaftid, green slimy thing with eight legs and a seahorse-like face, spits acid, used during the Animorphs' raid on Frank's Crazy Safari Place
Book 24: I think he morphs that unidentified orange monster in this one, when he briefly teams up with the Animorphs. Or was that the Galilash?
Book 29: Something during the Yeerk Pool finale
Book 30: Chameleon-crab-like creature used for mountaintop battle with Visser One
Book 38: Unidentified morph, something small used to escape
Book 45: Bievilerd: Used during Yeerk Pool rescue mission, quickly shot down by Bug Fighter
Book 47: Fire-breathing monster from Book 1
Book 48: Multiple morphs, including jelly thing, for battle with Rachel
Book 50: Black squid-like monster with red eye and a bunch of tentacles for the battle outside the hospital
Book 52: Some creature with tentacles, lurks in Yeerk Pool just before it gets blown up