Hear a lot about these on the forums. Can anyone explain them? Here's what I know:

There are three spells (aura/barrier/shield) and there are wands, talismans, etc out there that will apply these. Some sort of damage reduction? Shield seems to just be -AC, but is there more to it than that?

I *think* some of these items are limited, and some are specific to individual characters...and that there is something to do with finding your own sleeks. There are edges, I think, to locate these (Aura Attunement, etc) but I'm not sure what the level requirement is, and if this is how people usually find them.