Since a Unicorn Horn is specifically named as a +3 Magic Weapon, can a Weapon Augment Crystal be attached to it?
1\$\begingroup\$ Welcome! You can take the tour as an introduction to the site and check the help center for further guidance. Good luck and happy gaming! \$\endgroup\$– SdjzMay 27, 2019 at 17:56
Yes, you can.
Depending on the rank of augment crystals, they can be attached to an object of masterwork quality, enhancement +1 or enhancement +3. Because the unicorn's horn is treated as a magic weapon with enhancement +3, any weapon augment crystal can be attached to it.
Furthermore, it is not specified, that the weapon must be a manufactured weapon, so it should be possible to attach an augment crystal even to natural weapons, as long as they have proper enhancement bonus.
\$\begingroup\$ The only catch is getting natural weapons to be masterwork.... \$\endgroup\$– nijinekoMay 28, 2019 at 1:19