[1.6.7] Artifacts with "Poltergeist's" in the name?

[Jurriaan]

After clearing a vault in Dreadfell, I suddenly see in my inventory

Poltergeist's Colaryem
Poltergeist's Spectral Blade

In the log I read

Character killed Poltergeist Colaryem!

Are artifact names changeable like this?

[Zizzo]

That's from the "living-weapons" vault that was apparently way too common in Halfling Ruins before 1.6.7. Generally at least one of the opponents in the vault will be an animated artifact weapon (the "Poltergeist" opponents you saw), which will drop a copy of the corresponding artifact weapon with its name munged as you've seen (and I think a few ego tweaks, if I'm reading the code right). And this apparently bypasses uniqueness checks; I've got one character with both a Tirakai's Maul and a Poltergeist's Tirakai's Maul, obtained within a few levels of each other.

[GlassGo]

Aso you can get corrupted fixed artefacts in areas spawned by tentacled trees - I got Steam Powered Helm that had different name and was stronger then usual.