Hey, so this is something I was thinking of working on - probably won't be starting on it too soon since I still have some other stuff on the backburner (Ars Goetia demons, finish up the good/evil biome lore and creature descriptions, and also races to go along with the cave/biome revamp setting) - still wanted to write some of my thoughts on it down and get some suggestions.
Some spoilers below if you care.Essentially it'd be an addon mod rather than a total conversion, so you'd still have the regular vanilla races plus whatever other modded creatures you may have. I think I should just use my main pack's material, body detail plan and tissue files since they should already have everything that could be shared with the Diablo creatures - only things I'd have to do in that case would be to make the body plans and inorganic materials for spells and so on.
For the creatures themselves, most would probably just be wild predators in normal, savage or evil biomes. Some would require renames to prevent confusion with vanilla creatures (or ones from my other packs since I dislike having identical names for creatures between mods) - i.e the wendigos, the yetis or the imps - I don't think it should be that much of an issue since the games do have stronger/weaker variants that provide alternate names.
In regards to the variants (i.e the Fallen have a stronger variant called Carvers, as one example) themselves, I was honestly thinking of foregoing most of them since DF doesn't really do the gamey aspect of "this is a stronger version of X" that well.
I thought of only making exceptions for the ones that are found in radically different environments - i.e the regular wendigo variant was found in a temperate forest area where the Act 1 of Diablo 2 takes place - its Crusher variant was found in Act 2 which was a desert, and meanwhile the Wailing Beast was found in ruin areas of Act 3, which was more of a swampy area - so those 3 could be split up in this way.
I don't think there's that much potential for megabeasts with this, admittedly. Most of the creatures that'd fit for that would be better off being relegated to rare wild beasts that are also innate pets for some of the races or as castes for civilized races.
I admittedly don't have D3 experience so the lore stuff on it may be off. May change if I decide to get it, however.
For the races themselves, I have this list currently, some I'm not entirely sure on, though:
-Fallen - an absolute must-have - dark pits dwellers, would have the Shamans and Overseers as more rare, tougher castes, and the Hounds as pets.
-Khazra/Goat Men - would be split up into three types - Moon Clan (Moon Khazra as a naming scheme, perhaps - would extend to the other two clans), which would be the basic type thats seen in forest, swamp and grassland areas; Ice Clan, an undead variant thats immune to cold damage and has some other advantages, found in arctic regions; and Blood Clan, a mutated variant, in shrublands and mountains. Not sure what their sites would be - forest retreats most likely - all would have a "shaman" variant as well.
-Sand Raider - four-armed desert-dwellers - classified as demons and with improved physical attributes, but perhaps relatively limited armor and no shields. Town sites? Mummies and Beetle Demons could perhaps be found as their "pets", with Greater Mummies and Blunderbores as their "allied races".
-Zakarum - swamp-dwellers. Would have four castes - regular zakarum (zealots), priests, council members (like Geleb Flamefinger or Toorc Icefist), and perhaps a caste to represent Mephisto (considering in D2 he's found possessing a zakarum priest). Towns as a site type seem the most fitting.
-Corrupted Rogue - make town sites in temperate forests and grasslands perhaps. Aside from the regular human-like rogues there could be more demonic and corrupted variants that are stronger (seeing how some of them seem to have
spikes growing from their bodies and horns on their warped-looking heads - it could just be armor or some type of helmet but it's really hard for me to tell given how small the sprites are. Perhaps also a variant to represent Andariel's look, as she was the one that corrupted the sisterhood in D2. Not sure what the "male" caste would be, since atleast one is required for a civ to show up in worldgen if the race isn't entirely genderless.
-Claw Viper - desert race - towns or fortresses maybe?
-Lacuni - those cat-people from D2 and D3 - desert dwellers. Town sites? Could have some of the desert-dwelling Diablo creatures as pets, i.e leapers, vulture demons or dune beasts.
-Fetish - small demonic beings, found in D2's Act 3 - would translate to tropical forests and wetlands. Forest retreat sites would be fitting. Shaman variant could resurrect other Fetishes.
-Dark Cultists - cultists from D3. Town civ? Would have several variants, i.e Dark Vessels, Dark Berserkers, Blood Cultists (the deformed ones from Vidian's cult), Wretched Hosts, the Reborn, also castes to represent Maghda and Vidian. Various undead as pets, i.e Risen Dead, Grotesques or Wretched Mothers.
-Angels - self-explanatory - a friendly civ for once. Town sites I'd guess?
-Reapers - hostile angels from Reaper of Souls - multi-caste, i.e Punishers, Anarchs, Winged Assassins, Death Maidens, Ghastly Seraphs, etc. Revenant soldiers, Executioners, Westmarch Hounds (Reaper Hound as a name, maybe) as pets.
-Abyssals - those naga-like humanoids from D3. Cave civ? Two variants - regular abyssals and "callers" as a magic-user.
-Bogans - tusked humanoids from D3. Town civ? Two variants - regular quilled Bogans, tusked and larger Bogan Brutes.
-Unclean - cannibalistic barbarians from D3. Town civ.
-Morlu - reanimated warriors from D3. Town civ? Would have a regular variant and a caster variant. Corrupted angels as an "allied race".
-Flesh Golem - intelligent artificial constructs from D3, with 3 variants - Gorgers, Shamans and Hurlers. Town civ?
That's more or less the entirety of the "concrete" ideas - I was also thinking of four demonic factions to represent the forces of Diablo, Baal, Azmodan and Belial. Belial's more easy to think up of with the snake-like Deceiver demons from D3, and Azmodan too to an extent with the Demon Troopers he's often associated with, but I'm not too sure about the others.
My current ideas would be for Azmodan's force to have some of the demons he's associated with in D3 as castes - demon troopers as the "basic" most common caste, the D3-style succubi as another, Colossal Golgors as a large "brute" caste, Phasebeasts, Heralds of Pestilence, as well as representations of Azmodan's Lieutenants and Azmodan himself - similarly for Baal's forces - aside from Baal himself, also stuff like Demon Imps, Stygian Furies, the D2 style Succubi, Baal's Minions (called "Enslaved" per their basic variant), Blood Lords, Death Maulers, Overseers, a caste to represent Baal and perhaps one to represent Duriel as well, considering he was guarding Tal Rasha's tomb.
I'm not too sure about Diablo's forces - I guess some of the D1 and D2 Act 4 demons would be the castes in that case - Hidden, Megademons, Horned Demons, Oblivion Knights, Overlords, Lightning Demons, Blood Knights (those demonic knights from D1 - name from one of their variants, as Hell Knight I've used for the Doom-style Hell Knights), D1-style Succubi, Magi (from D1 - perhaps called Cabalists on one of their variants), a caste to represent Rakanoth and a caste to represent Diablo (perhaps a variant to represent his D3 look which had four arms and a rather distinct figure). Think my main issue is the "race" name for these factions, since I wouldn't want to go with "demon" as it could lead to some confusion. I guess something like "minion of destruction/terror/lies/sin"? Not fond of that either as there's an actual creature called "minion of destruction" in the D2 expack.
I'd probably include some concept art-only creatures as well, like I've done with my Warcraft mod and what I'm planning to do with the Dragon's Dogma mod (either as separate ones or as castes for existing creatures, i.e Azmodan had an early two-legged concept which I could make into a separate caste for his faction).
Lastly, I'm not sure if I'll make the different human groups into separate civs, i.e the barbarians or the Vizjerei. Perhaps as an optional addon like the Kingdoms of Humanity addon for my Warcraft pack.
Anyway, sorry if its a bit of a long read - I'd definitely appreciate any thoughts or suggestions. There's probably gonna be a lot of stuff that I won't be able to do due to DF's limitations (i.e no suicide creatures like Fallen Lunatics or frenzied Baal's Minions) but I'll definitely want to do as much as is possible.