I've been experimenting with DLTCEP recently and decided to take a stab at creating a Staff of Withering from the 1e and 2e DM guides. I managed to get all of the effects and icons I wanted in place (through lots of trial-and-error, of course) and it seems to works perfectly in BGEE.
Since the effects of aging and limb-withering aren't implemented in BGEE, I've attempted to compensate by giving the staff the power to (temporarily) drain the physical ability scores from its victims. Although the PnP Staff of Withering withers limbs and causes aging permanently, I thought this would be much too OP for BGEE. Instead, I decided to make it a moderately-powered magic item. Here are the basic details for the staff's powers (please feel free to post suggestions or comments):
Staves of Withering are rumored to be crafted by the Cult of Velsharoon in the charnel houses of Skull Gorge. While their motivations for creating these macabre weapons remain unclear, the Archmage of Necromancy must have dark plans, indeed.
Those struck by a Staff of Withering suffer a progressively enervating fate. Each hit drains its target's vitality, rendering it weaker and less agile until collapsing a lifeless husk. Victims that survive an attack regain their vigor soon afterwards, although with a more "intimate" understanding of the twilight between life and death--perhaps what the Lord of the Forsaken Crypt intended.
THAC0: +1 (non-magical)
Damage: 1d4+1 (crushing)
Special: Drains the target's Strength, Dexterity, and Constitution scores by 1 point cumulatively upon each hit (no save). When any ability score reaches 0, the target dies. The target must also save vs. Wands with a -2 penalty or be slowed. The draining and slowing effects of the staff cannot be dispelled, but wear off after 3 turns for those who survive.
Wielders of Staves of Withering (and their parties) do not gain experience points from deaths caused by its ability-draining effects. Experience is awarded only if the target is killed by by the staff's crushing damage. Candlekeep sages speculate the staves are enchanted to transfer the experience by some nefarious means to Velsharoon and his clergy.
Creature Immune: Undead (-15 to hit) and Outsiders
Speed Factor: 2
Proficiency Type: Quarterstaff
I found that the 1e version of the staff was limited to Clerics only, but the 2e version is usable by any class, so I decided to make it usable by Cleric, Druids, Mages, including all Specialist Wizards except for Illusionists (since the staff is empowered by necromantic magic). I can only imagine how OP the staff might become if it were usable by Kensai and Fighters. Since Clerics, Druids, and Mages/SWs have relatively weak THACOs at low and mid-levels, using the staff against difficult foes might be more of a liability (especially those with high ACs), given that it has only a +1 to hit bonus (which is non-magical--it was the only feasible way to restrict the staff from being used against outsiders and magical creatures).
The PnP staff has charges, and therefore is expendable, but I decided to make it a permanent item (hence the price). I'd be interested in hearing what people's thoughts are on that as well.
For the effects, whenever a creature is hit by the staff, it plays a brief, haunting sound (which I believe is from the one of the crypts in BG or BG2) and causes the victim to turn semi-transparent for a couple of seconds (which is supposed to symbolize their sudden loss of vitality). And, of course, the staff is black. ^.^
*The updated (v 1.5) item mod is attached below in RAR format. Thanks for @Alkalurops
for making this mod WeiDU-compatible and @Cahir
for the Polish translation.
*Update 03/29/15: The save penalty vs. slow has been corrected to -2 (it was previously set at -4).