Antimagic and Runes

[Hakko]

I'm running a Wyrmic with Anti-magic: Link

He completed the Temporal Rift quest and picked up the artifact rune. Every time I try to use it, however, I get a "The rune interferes with your antimagic abilities. The spell fizzles." This is in contrast to the shielding rune I had earlier in the game, which interfered with my antimagic abilities but still worked.

Bug or feature?