Aside from this edge sounding bad ass, what all does it do--and what's it take to get it?

The help file suggests greater resistance to being knocked out, less bleeding, and maybe less likely to get broken bones and such.

But it only hints at the downsides (things that are restrictive or weaknesses of elementals). I'm curious what this means because each type of elemental is going to have it's strengths and weaknesses, so how does that combine into one?

Any taken it that can summarize and describe whether it seemed worth it as being quite costly?

Anything in particular necessary to get it other than edge points? I get no prereqs when discussing with the guildmaster.

Thanks.