No. 1 is a Seer, No. 2 and No. 5 are werewolves, and No. 7 may be a wizard.
Someone died on the first day, indicating that the wizard held both antidote and poison. Two people died the next day, indicating that the wizard used poison. We know that No. 2 and No. 7 are different camps.
If 7 is poisoned to death, the wizard believes 7 is a werewolf and that 2 is Seer. Then the wizard will prioritize using the antidote to save 2 instead of using the poison to kill 7. So No. 7 can only be killed by a werewolf. Then No. 2 is likely to be a werewolf. If No. 7 is not a wizard, then the wizard sees that No. 7 is killed by a werewolf and will choose to save No. 7 instead of Poison 2. Therefore, No. 7 is likely to be a wizard who cannot save himself, so he decides to poison No. 2 to death.