Buffy.

Giles looked at Xander before turning to Buffy and saying, "I'm afraid that the only person who can possibly handle this spell and avoid being corrupted is Buffy due to the fact that she's the slayer."

"I see," Xander replied hiding his disappointment at not getting the chance to prove his worth.

"Why am I the only one that won't be corrupted by this spell?" Buffy asked in confusion.

"Yeah why is she the only one that could do this?" Willow agreed wanting to know why she couldn't handle that power.

"Due to the nature of this spell Buffy would be the only one who could do this without getting corrupted by the dark magic," Giles replied before explaining why Buffy would be capable of handling this spell. "The spell forces magical energy into a person similar to the way a possession works and due to Buffy being the slayer she's immune to possession. As for myself and Willow well we would become almost invincible with all that power running through us and it would corrupt us very easily."

"What about Xander couldn't he handle it?" Buffy asked.

"Xander has been possessed before and because of that he would likely be overwhelmed by the spell that's why he can't be the one to do this." Giles explained getting nods of understanding from everyone.

"Well," Xander said with a huge false smile on his face. "Now that that's settled when do we do this?"

"We can do it right now, no one should bother us here due to it being after school so lets get started." Giles replied getting ready to do the spell.