3) On the other side, there are some conversions that were so frustrating that they became amusing. One that still comes up 3 years later started innocently enough as the fairly simple
mold wyrm quickly spread into over 300 posts, as well as three more templates (the
false keraptis,
subsumed mind, and
skin puppet) and another unique monster,
Mossmutter.
Oh boy, I remember well that little rabbit hole from
Return to White Plume Mountain!
If I recall correctly, the wizard Keraptis left behind a number of cursed scrolls, which, when read, caused the victim to believe that he/she/it was the real Keraptis (thus gaining the False Keraptis template). These false Keraptises have the ability to imprint other creatures with parts of Keraptis's mind (causing them to gain the Subsumed Mind template), creating a distributed hierarchical mind under the control of each false Keraptis.
Add to this already complicated back-story a new creature billowed forth from Bruce Cordell's mind called a mold wyrm. These are huge fungal creatures created by a leaking Basin of Boundless Life. Creature consumed by mold wyrms return to life as mold wyrms themselves. Now take a particularly large specimen of mold wyrm, and have it ingest a gnome wizard, who has previously had the misfortune of becoming a false Keraptis. Upon being devoured by the mold wyrm, this particular false Keraptis managed to reseat its (false) mind into the mold wyrm, creating a new, unique example of a false Keraptis named Mossmutter.
Like other false Keraptises, Mossmutter can imprint on other creatures, but it does this in an unusual way. Instead of becoming new mold wyrms, the creatures Mossmutter kills become Skin Puppets (gaining the final template). Each of these is a fungal mass inhabiting the creature's former skin and adding to Mossmutter's hierarchical mind.
I remember Shade being particularly tenacious about making sure the conversions did justice to Cordell's original vision of how all of these creatures fitted together. That process resulted in one new creature, three new templates, three sample creatures for those templates and one new unique creature. Along the way, we even got to revisit the sword Blackrazor from the original
White Plume Mountain, now in the possession of Killjoy, an efreet False Keraptis. Even though the complexity of that project was a but frustrating at the time, I think the end collection of templates and creatures really holds together well. (And, IMHO, does a better job of modelling the hierarchical minds than the original adventure.)