This item was in the dungeon I threw together for our 1st edition AD&D last week:
This huge instrument stands ten feet tall, is made of silver with platinum strings, and weighs at least a ton. A low musical hum emanates from the strings and the entire thing radiates strong magic. Anyone sleeping overnight within ten feet of the haphazard harp has his or her healing rate doubled.
Those who dare strum the strings will be affected by the harp’s magic as follows:
1. -1 INT
2. -1 DEX
3. -1 CON
4. 2d6 damage
5. 1d6 damage
6. -1 to STR, WIS, or CHA and +1 to INT, DEX, or CON (player’s choice)
7. 2d6 damage and +1 to one ability score (player’s choice)
8. Heal 2d6
9. +1 STR
10. +1 WIS
11. +1 CHA
12. Gain one level of expereince
The harp can only affect one individual once, though the healing benefit always works. It may have a limited number of charges before it teleports away to another location in this world or another, or perhaps it loses its powers if removed from the place where it is found.
One character raised her WIS to 19 with it, another lost a point of CON and the bonus hit points that came with it.