Voldemort didn't use Avada Kedavra on Snape because he believed he couldn't cast the Killing Curse with the Elder Wand to kill its master. He was convinced that to truly master the Elder Wand and wield its ultimate power, he needed its allegiance to switch to him.
Voldemort's Misconception About the Elder Wand
Voldemort sought the Elder Wand, one of the three Deathly Hallows, believing it would make him invincible. After acquiring it, he found its power to be inconsistent, leading him to conclude that its allegiance had not fully transferred to him. His understanding of wandlore, while extensive, was fundamentally flawed in this critical aspect.
He mistakenly thought that Severus Snape was the Elder Wand's true master because Snape had killed Albus Dumbledore, the wand's previous owner (as Voldemort understood it). According to Voldemort's reasoning, for the wand's allegiance to shift to him, the current master (Snape) had to be defeated.
The Allegiance Dilemma
The Elder Wand's allegiance is not earned simply by possessing it, but by defeating or disarming its previous master. Voldemort believed that killing Snape would make him the Elder Wand's new master. However, he faced a critical dilemma:
- He needed Snape dead to secure the wand's allegiance.
- He knew he couldn't use the Elder Wand itself to kill its master (Snape, in his flawed perception). Using the wand against its own master would essentially make it refuse to perform the act, or at least perform it weakly.
This paradox meant Voldemort had to find an alternative method to eliminate Snape without using the very wand whose allegiance he sought to win.
Nagini: The Chosen Instrument
To bypass this perceived limitation, Voldemort chose his loyal serpent, Nagini, to kill Snape. By ordering Nagini to deliver the fatal bite, he believed he was performing the "defeat" necessary for the Elder Wand's allegiance to transfer to him, without directly violating the wand's loyalty to its perceived master.
| Event | Voldemort's Belief | Reality |
|---|---|---|
| Snape's Death | Would make Voldemort the Elder Wand's master. | Did not make Voldemort the Elder Wand's master. |
| Elder Wand's Master | Snape was the master because he killed Dumbledore. | Draco Malfoy was the master because he disarmed Dumbledore; Harry Potter became master by disarming Draco. |
| Method of Killing | Nagini was necessary because the wand couldn't kill its master. | Nagini's actions were irrelevant to the wand's true allegiance, which was with Harry. |
The True Master of the Elder Wand
Ultimately, Voldemort's plan failed because his understanding of the Elder Wand's allegiance was incorrect. Snape was never the true master of the Elder Wand. The wand's allegiance had shifted to Draco Malfoy when he disarmed Dumbledore, and then to Harry Potter when Harry disarmed Draco. Therefore, killing Snape was a futile act in Voldemort's quest for the wand's ultimate power, as the wand's loyalty was already with Harry Potter.
