Current ebuild does not support amd64 platform for games-strategy/heroes3. I've attached a modified ebuild with such support.
Created attachment 314285 [details]
heroes3 ebuild with support for amd64 platform
This bug is related to bug #372091 though that bug was closed, so I don't hope games@gentoo guys to pay much attention to it hence I've created this bug report.
I don't have the game but it seems like at least a good place to work from later if it's not exactly right. in portage.