These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.04 s (backtrack: 0/20).

[ebuild  N     ] dev-games/irrlicht-headers-1.8.5::gentoo  21321 KiB
[ebuild  N     ] dev-games/irrlicht-1.8.5::gentoo  USE="-debug -doc" 0 KiB

Total: 2 packages (2 new), Size of downloads: 21321 KiB