ports/games/multimc/pkg

The defaults of multimc are set up to play the most recent release of
Minecraft.  Older versions of Minecraft can still be played, with some
optional settings.

To play Minecraft 1.12 and older:
# pkg_add lwjgl jdk%1.8
Add the instance you wish to play, then Edit Instance | Settings
and change Java installation to use /usr/local/jdk-1.8.0/bin/java