/usr/lib/x86_64-linux-gnu/OGRE-1.8.0/Plugin_ParticleFX.so is in libogre-1.8.0 1.8.0+dfsg1-7+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/OGRE-1.8.0/Plugin_ParticleFX.so.1.8.0