It looks like a variation of the idiom give an arm and a leg:
give an arm and a leg (for something)
- To pay, give, or do whatever is necessary or required. They had to give an arm and a leg for the lawyer they hired. I had to give an arm and a leg just to get an interview for the job.
- If you say that you would give an arm and a leg for something or to do something, you mean that you want it very much. I'd give an arm and a leg for a cup of tea. Any jazz professional would give an arm and a leg for half an hour playing with Wynton Marsalis.
In other words, other followers really want to do those tasks, or they would do anything necessary to be able to do those tasks.
Apparently, this is from Harry Potter and the Goblet of Fire. According to @Alex (*spoiler alert*), the statement foreshadows actual hand sacrifices.
In other contexts, other variations could be made, like "give your right leg". A crude example I've heard would be "I'd give my left/right nut for [something]", nut being slang for testicle.