In my headcanon Wyll's vanilla body shape is something he had before meeting his patron. And after that - things gone wild.

What this mod does:
1. Changes Wyll's body shape to a more hunky variant (body shape 4) - his open air diet and trainings paid off. Portraits are changed as well.
To avoid spoilers - i wont describe, what  are the requirements to gain some of Wyll's forms.
2. Changes Wylll's hellish form visuals into true tiefley: fat horns, spiky skin, subtle spots all over body and face, his eye color is now more dramatic: one eye is yellow-red, one eye is bright blue.
Nice tail and curly hair come as bonus.
3. Since Wyll has very low strength - i've added a ring, that slightly increases this stat. It can be found in his inventory when playing him as an origin or it can be bought through vendors.

Everything in this mod is vanilla assets, except hunky heads - they r my remeshed versions of the vanilla.

Warning (read this before installing this mod!):
1. This is beta and very possibly it will stay so. I use this mod for my own fun but its also a proof of concept.
Issues:
1) body animations can be clunky - its a vanilla issue when altering shape. I wont fix it.
2) face animations - sometimes it looks like MassEffect Andromeda horrific flashbacks, if u know what i mean. Dont know, if it can b better.
3) body textures - ive managed to preserve everything, except his body scars. Dont know, if i can fix it.
4) face textures - at certain angles u will see seams. It can be fixed, but i dont know, if ill want to.
5) when leveling up - his eyes show only one color at a time. Not a big deal.
6) cinematics - intro doesnt work properly, as for the others - i need more time to test.
7) teeth in human form - they are somehow duplicated - even if i delete the mesh. Trying to solve this. fixed in 1.0.1
2. This mod replaces vanilla assets - strong head H for male humans and strong head A for male tieflings.
When uninstalling this mod everything should work in its original form.
3. Be aware - since patch 5 mods are baked into your saves, so as for now - there won't be nice and clean way for you to disable this mod. Though there is a file that reverts Wyll to his original looks in the optional section: use it - in case u'll want to revert to some sort of unmodded state.
4. Remember to always make saves before installing anything. 

This mod can also be used as a modders resource - since ive added interesting lines in the Wyll's looks code: like body tattoos.
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Installation:
Extract pak file in this directory:
C:\Users\Username\AppData\Local\Larian Studios\Baldur's Gate 3\Mods

Credits to:
for the tutorials
Padme4000
I'm A Doctor Not A
MUNMOMUU
Weeviljester
Codexa
and many others
for enhancing game's visuals with reshade preset (i use modified version, but the original one is still very beautiful)
accidentProlenol
for the wondrous multitool
ShinyHobo