Kalphite lair is just west of a fairy ring.
For this task, there are 2 options. Either go for the weak kalphite workers, or the much stronger kalphite soldiers. I started on the soldiers, but their drops were very bad, so decided to just get the task done by using workers.
No damage taken from them, but no good drops either.
Image is from soldiers.
Alternatively, soldiers can be ranged, but this is tricky, as they have quite high defence.