The Wondrous Wand of Unreliable Resurrection usually works right and can bring that fallen comrade back from the dead. Note usually. The total number of Hit Die of creatures that the Wand has returned to life is the percentage chance that it will malfunction. When found in a loot pile, the Wand will have already been used for at least 3d10 HD worth of resurrections. Of course, the DM can adjust that however they will.
So what happens when the Wand malfunctions? Roll 1d8 below and see.
1. Disintegrated: That’s all folks!
2. Animate Dead (as the spell): Oops. Sorry. But at least your friend will be worth a few XP.
3. Lost in the Transition: Randomly rearrange the character’s ability scores.
4. Sorry, Wrong Number: The wrong soul is summoned from the Underworld. Make adjustments to alignment, class, ability scores as necessary.
5. Freaky Friday: The fallen character is brought back to life but the wielder and target switch bodies.
6. Reincarnation (as the spell)+Gender Switch: Hiya doin’?
7. Reincarnation (as the spell): Could be worse?
8. This Has Never Happened Before: The wand just doesn’t work. No effect but still counts to total HD resurrected.

What happens when the Wand reaches 100 HD? It continues to work but will malfunction every time. If this seems too kind then change result 8 to 10d6 Fireball, the wand explodes and is destroyed.
Keep rolling those dice folks!