FREQUENCY: Very rare
FREQUENCY: Very rare ([Dungeon Level VI])
 

NO. APPEARING: 1-4 <(01-60%=female, 61-00%=male)> <(10% of the time, add 2-12 huge (M) spiders)>
ARMOR CLASS: 3
MOVE: 12"
HIT DICE: 6+6
% IN LAIR: Nil
TREASURE TYPE: Individuals [N] (x 2), [Q]
NO. OF ATTACKS: 1
DAMAGE/ATTACK: By weapon type or 1-4 <(THACO 13)>
SPECIAL ATTACKS: Spells, paralyzation
SPECIAL DEFENSES: Nil
MAGIC RESISTANCE: 15%
INTELLIGENCE: High <(13-14)>
WISDOM: 4-16, min. 9 if female <DMG.79: added this line, link to PH>
ALIGNMENT: Chaotic evil
SIZE: L
LEVEL/X.P. VALUE: VI | 875 + 8

The drider is a creation of Lolth's magic.
When drow of promising ability reach 6th level or slightly higher,
Lolth will summon them and put them through a specially-designed test.
The drow that fail become driders. <noted at UA>

A drider appears to be a cross between a giant spider and a drow.
The torso, head, and arms of a pale,
bloated drow sprout 8 spider legs.
Due to the bloated form,
it is impossible to distinguish the sex of a drider,
but 60% of those encountered will be female.

A drider retains whatever drow abilities it possessed before the transformation;
therefore,
all driders have magical or clerical ability,
the type depending on whether they are male or female. <gifs could be used>
Female driders have clerical abilities equal to a 6th or 7th level cleric;
<links to PH, or random generator>
male driders have the magic ability of a 6th, 7th, or 8th level magic-user.
<I13-14 is the same for purposes of MU spell casting>
<>

<alt of above>
Female driders have clerical abilities equal to a Canon or Lama (C6 or C7);
male driders have the magic ability of a Magician, Enchanter, or Warlock (MU6, MU7, or MU8).
<I13-14 is the same for purposes of MU spell casting>
<links to PH, or random generator>
<>

In addition, a drider has the natural spell ability <technically, spell-like abilities> of a drow and is thus able to cast the following spells 1 per day: <alt>
    dancing lights, darkness, detect magic, faerie fire, know alignment, and levitate. <clerical or magical?>
Female driders can also cast [clairvoyance], [detect lie], [dispel magic], and [suggestion] spells once per day. <spells? spell-like abilities?>

In combat,
all driders fight as 7 HD monsters,
typically using swords or axes, <random sword & axe generation table?>
though many carry bows strapped to their backs. <random bow generation table?>
A drider may also attack with its bite (for 1-4 points of damage).
Those bitten must save vs. poison at -2 or be paralyzed by the drider's spittle for 1-2 turns.

Driders are outcasts from drow communities and thus bear them no great love.
They are seldom found in numbers,
preferring to work alone.
Driders will be accompanied by 2-12 huge spiders 10% of the time.
Generally living underground,
they will often stalk their victims until the right opportunity for a kill presents itself.
Their diet consists mainly of the blood of their victims,
as they have acquired a spider's tastes.
 

by David C. Sutherland III

Dave Sutherland created the drider for Q1 and attributed it to Lolth, so that was that.