Anyhow, here's the relevant extracts from The Great Modron March:
Modronoid Xaldra
The first Modronoid encountered by the PCs is a buddy of theirs who vanished during a night of revelry and reappeared as a monstrous cyborg thing! She'd been kidnapped by thugs hired to get "experimental subjects" for the modron-grafting research of the mad wizard Valran Stonefist.
From Page 56:
SNIP …the characters hear a strange dragging and hissing outside their door. A moment later, something heavy and metallic strikes against the door, knocking several times. Before they can answer, the door bursts inward, revealing a gleaming thing with pieces of flesh squeezed between metal plates. Crazed eyes stare at them and blades slowly extrude from its arms. The creature has Xaldra’s form underneath the metal — but the barmy look in its eyes tells the PCs that there’s nothing left of her mind in this thing.
The Xaldra-creature attacks them immediately, howling its fury and dismay. In its agony, it mistakes the PCs as the source of its anguish; it fights to the death, wanting only to slay them all or be released from this state.
MODRONOID XALDRA: AC 2 (metal plates); MV 9; HD 6; hp 31; THAC0 15; #AT 2; Dmg 1d6+2 (arm blades); SW metal-affecting spells; MR 10%; SZ M (5′ tall); ML fearless (20); Int average (10); AL CN; XP 420.
If the modronoid’s killed, the metal parts fade away, leaving only the mutilated body of Xaldra behind. Her eyes don’t even look like they’ve found peace. The creature can be incapacitated, but the PCs need to find a way to keep it unconscious. If they allow it to wake, it immediately attacks again. There’s no way to communicate with Xaldra’s spirit either — the modron-working that’s been foisted on her body seems to have driven the spirit from her flesh already.
Now you might wonder why the metal parts of the Modronoid vanish when it dies. Well the answer is… disturbing. Those parts are grafts from a Base Modron who is still alive. The life force of the unwilling modron donor and the humanoid host are surgically linked, so if one dies so does the other. Since the Modron is an extraplanar outsider, if it dies its body vanishes, including any severed parts grafted onto a Modronoid.
Turning a Humanoid into a Modronoid normally drives it insane. Crazed modronoids tend to try to kill themselves, attack everyone they meet, and pace like rabid wild animals (see 10b Modronoid Prison and 8 Prison, below).
However, there are ways around this "modron madness," for example, Xaldra can be restored to sanity by restoring her memories and mind, which presumably also somehow returns the spirit which was driven "from her flesh"…
From Page 58:
7. SENSORIUM: Like a smaller version of the Sensates’ sensoriums in Sigil, this room holds dozens of recorder stones, filled with Valran’s experiences and those of his guests and victims. The PCs can find Xaldra’s memory-stone here, sparkling like her personality… SNIP.
If the PCs’ve brought the modronoid-Xaldra here, they can place the stone on her chest and her memories will slowly filter back into her. This restores her mind, but her body remains twisted and partially metallic.
The madness can be "fixed" by a modron brain graft, as explained by the Modronoids' creator Valran Stonefist below (see New Modronoids).
Original Modronoids
The following encounter Locations relate to the first batch of Modronoids, which included Xaldra. Note how the Modronoids have identical stats despite being made with grafts from three different ranks of Base Modron (pentadrones, tridrones and monodrones).
From Page 59:
10B. MODRONOID PRISON: Though Ildurn informed the PCs that 10 of these creatures existed, he was wrong. Three of them perished during the day, having succumbed to modron madness and taken their own lives in moments of lucidity. The remaining creatures are thoroughly restrained by a massive web spell. One of the modronoids has been steadily sawing through the material, and they’ll all burst free when the PCs confront Valran. If they’re freed before that, they immediately attack.
The modronoids strike at anyone in their path. They have no fear of anything — death only offers them release.
MODRONOIDS (7): AC 2 (metal plates); MV 9; HD 6; hp 31 each; THAC0 15; #AT 2; Dmg 1d6+2 (arm blades); SW metal-affecting spells; MR 10%; SZ M (5′ tall); ML fearless (20); Int average (10); AL CN; XP 420 each.
10E. MODRON PRISON: The captured modrons are kept here — both the whole and dismembered ones. Valran does his best to ensure that all his prisoners are treated well, even those that’ve already been mutilated to serve as parts. He’s well aware that his process links the life force of the modrons and the humanoid victims: When the humanoid host dies, so does the modron whose pieces are grafted on to it. If the modron manages to expire first, the host dies as well. Valran’s learned to combine only one modron with one host; it cuts back on the possibility that a deceased host or modron will destroy a whole batch of experiments.
Valran keeps the modrons from acting as a unified whole by “recruiting” modrons separated by more than one caste, which prevents them from communicating with each other. He currently has five monodrones, three tridrones, and one pentadrone. Xaldra’s metal parts were taken from one of the tridrones.
New Modronoids
Considerable later in the adventure, the PCs discover Valran Stonefist in a decaton's body who reveals he has invented an improved version of the Modronoid that is often sane enough to follow orders! Fortunately for the party, all these New Modronoids are away on various tasks so the PCs doesn't have to fight any. Still, it would have been nice to have seen if their stats were any different from the insane Original Modronoid described above.
From Page 107 & 109:
Valran explains. “As you know, I’d been working on transplanting living humanoid minds into the shells of modrons, making the best of both worlds, as it were. By keeping a piece of the modron brain within the body, not only do we cure the modron madness, we also ensure that there’s a build-in tendency to follow orders in the new modronoids. Of course, it tends to slow down the mental processes of some bashers, and it still drives others completely barmy, but that’s a small price to pay for an army of creatures like this, eh?”.
From Pages 109-110:
2. MODRONOID BARRACKS: This petal houses most of the modronoids. When the PCs show up, the modronoid force is out scavenging materials and supplies for the Flower, so they won’t play a direct part in this adventure. The room is littered with odd personal effects, but the litter is strangely ordered, as if each piece had been purposely dropped in a specific spot. It’s as though the inhabitants were trying to assert their individuality while still conforming to a greater pattern.
3. LIFE SUPPORT: The pieces of the modrons that’ve been used for grafts hang here, some from chains, others in baths of sludgy goo. The setup’s devoted to keeping these modrons alive so the modronoids can continue their reign of terror. Twenty modrons hang here, and they twitch feebly as the PCs enter. Slaying these modrons frees their essences and kills the modronoids attached to their pieces.
8 PRISON: The prison contains many cells, and all of them are full. Some cells hold modronoids that haven’t yet reconciled themselves to their fates, SNIP, though the modrionoids pace like crazed beasts at all hours. SNIP
PCs here have no trouble picking out Crasad’s younger brother, Tairish. He’s been recently converted to modronoid status, and he howls with frustration and fury. If the PCs speak to him calmly and gently, they can soothe him and gain some useful information. SNIP
In a lucid moment, Crasad begs the PCs to kill him and then erupts into howling fury again. If the PCs don’t want to draw the attention of the guard, they’ve got no choice but to finish Tairish off or knock him unconscious. SNIP