/usr/lib/mono/4.0/PEAPI.dll is in libmono-peapi4.0-cil 2.10.8.1-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.0/../gac/PEAPI/4.0.0.0__0738eb9f132ed756/PEAPI.dll
/usr/lib/mono/4.0/../gac/PEAPI/4.0.0.0__0738eb9f132ed756/PEAPI.dll