MarsSeed [1] filed a deletion request for omniorb425 [2]:

This legacy version package is not needed anymore by other packages.
And it conflicts with the newer AUR/omniorb.

(Also the pkgname does not conform to Arch packaging guidelines, as
the attached number should mean major version, but this is not v425,
but v4.2.5.)

[1] https://aur.archlinux.org/account/MarsSeed/
[2] https://aur.archlinux.org/pkgbase/omniorb425/