Soul Stone

There are a several places in Factions to get these...
...Missions (post Shing Jea Island), a few Explorable Areas with a single Shiro'ken or two,
but by far the best place to farm them would be the Raisu Palace explorable area or its mission
since it is ALL Shiro'ken.
They're is no easy simple solo build here (well, maybe a Shadow Form style builds may do well, since Shiro'ken Mesmers can't remove enchantments, neither can their Necromancers btw),
so u may need to use a small (player+3 heroes) party,
either way its a relatively fast farm.

And that's all the advise I can give you on Soul Stone farming.
LOL, hope it helps...in some fucking way or another.
Atty