Illumisfhityroc is an exterior you can't miss when you see it, it's really very recognizable.
Its ability to create powerful (+4), time-limited items that you'll need to "buy" with 1000xp and 200 gold coins.

In BGEE/EET you'll find her in Beregost, then when you have access to Baldur's Gate she moves to the BG central place. Items created last 4 days.
In IWDEE you'll find it in Kuldahar. Items created last a week.

The rings, amulets and armors created by Illumisfhityroc are not magic items (they are psychic creations) and can therefore be worn in conjunction with real magic items.

List of items Illumisfhityroc can create :
Dagger +4 (including throwing ability)
Short sword +4
Long sword +4
Scimitar +4
Katana +4
Bastard sword +4
Two-handed sword +4
Axe +4 (including throwing ability)
Hammer +4 (including throwing ability)
Club +4
Mace +4
Flail +4
Spear +4
Halberd +4
Staff +4
Crossbow +4
Longbow +4
Short bow +4
Slingshot +4
Infinite bolt +3
Infinite arrow +3
Infinite bullet +3
Infinite dart +4
Besantine +4
Chainmail +4
Full plate armor +4
Bracelets of AC 1
Targe +4
Large shield +4
Ring of resistance to the elements 40%
Amulet of mental protection
Ring of physical resistance 25%
Cloak of resistance to magic 25%
Amulet of protection against disease and poison
Scarab of protection against death and the negative plane
Ring of free action (does not prevent haste)
Ring of protection +3
Ring of regeneration 1/5sec
Belt of strength 19
Bracelets of dexterity 19
Boots of super speed(+2 movement points, double movement, +1/2 attack per round)
ioun stone of AC +2


Update:
V2:
Price in xp reduced from 1200xp to 1000 xps.
Correction for EET where internal zone names are not the same.

v3:
+3 item icons for created items.
Fixed non-functional dialog under EET.
Added item list to the read_me.
Throw" and "melee" added to mixed weapons.
The cloak of magic resistance no longer has the text of a ring.