???

I came to the Wiki to find out the exact same thing on the exact same day haha. I am some tired of Maldron the Assassin's antics in Brume Tower...

Finally decided to test it, and it works haha!!!! The imortal possessed suit of armor made short work of the ***hole!

It is an online item in the sense that it affects online play (or simulation of it, as the NPC invaders are treated similarly, if not the same, as regular invasions in the code, with the exception that they can occur offline). An online item in Souls games does NOT mean, nor imply, that they ONLY work online. It means they affect multiplayer functionality in some way. For example - the ring that Shalaquor sells that lets you choose a "god" is meant to limit the pool of people that can summon you / you can summon. However, you can also just equip it offline for the heck of it, though it will quite literally do you no good. The same can be said for joining the Blue Sentinals, the Rat Covenant (though the ring from them is useful), the Covenant of Champions (though this has the additional effects of disabling ALL summons including NPC summons, as well as making enemies infinitely respawn as in every other souls game), the Blood hunters covenant (if thats not the name, I can't remember it off the top of my head... and this one ALSO has a ring that you CAN obtain offline even though this is a PvP covenant... but only if you use a bonfire ascetic in the correct place, or join in NG+), and most of the other covenants as the majority of them in DS2 are intended to either be Co-op or PVP functions. They're by no means online only, but you will only get the most (or ANY) use of them from online functionality tied to them.