Dark Souls

Praise the sun!

Shiva of the East
YoN9Vt2SwDk The NPC merchant Shiva of the East is a bit, uh, weird. You're told that he's untrustworthy, and killing him and his bodyguard is the only way to get one of the game's best rings...but unless you provoke him, you don't get any further than having him sell weapons in Blighttown.

Regardless, apparently he was intended to behave similarly to Satsuki in Demon's Souls – he asked you about the "Chaos Blade", and if you returned to him with it, he'd kill you and steal the sword. At this point, you'd get an unused Black Eye Orb that allows you to invade Shiva's world and reclaim the sword. Surprisingly, the invasion event still exists, and even kinda sorta works.