I've done that before, I made a staff that could cast the spells 'Stone to Flesh' and 'Disintigrate'
I haven't done this for a while so forgive me if I've got a few technical terms wrong.....
I opened Shadowkeeper and ran through the spells to find an appropraite icon that would be, well, appropriate! [img]tongue.gif[/img] I found "Fire Elemental Transformation" and exported it. I then opened it in "Spell Creator" and found the Icon to be called SpPr731C. Remember that....
Again we go to Shadowkeeper. Open "Creature Browser" and find the .cre name of the thing you want to shapeshift into. I found "Greater Fire Elemental" and looked at all of them. I chose "GORFIR01", remember that too.
Click on the little Dagger with a snake, and create a new extension header on the item you've made in IEEP. Copy SpPr731C into the "Use Icon" section. Now in the "Use Item" bit in the game it will display a picture of the icon for Fire Elemental Transformation. Now add these into the appropriate boxes: (Box names in Bold and Italics, contents normal)
Attack Type: Magical/None
Use Location: Magical
Target Type: Self or One Target, you didn't say whether you wanted it to be a targetable polymorph....
That should be all that matters. Now create a new "Item Effects" thing, and choose "Polymorph into Specific". Into the "Resource Key" thing put GORFIR01
The other effects her you can choose, for instance
Timing Mode would be "Duration" and
Effect Time would be however long you wanted the polymorph to last, in seconds.
You can now create however many other special effects you want, like maybe a few sound effects and visual effects to add to the transformation, by adding extra "Item Effects".
Voila! Save and you've got your item.
PM me or reply if you've got any questions about what I've said.