I just upgraded my 64-bit 14.2 system to -current, which was not without hiccups along the way since the system ran out of space. Resolved that and was able to get everything updated and running until I tried to update my multilib. the last thing I see before the system went to the crapper is

Upgrading glibc-2.30-x86_64-1 package using ./glibc-2.23_multilib-x86_64-4alien.txz

Looks like I forgot to blacklist, as well as point to the correct repository so my current glibc got messed up by an older multilib version. this did not complete, but was enough to make everything unresponsive. any suggestions on salvaging this or am I screwed? can't seem to run slackpkg, installpkg, etc

This looks like a version downgrade.
You should be able to recover by booting into a recovery system, chroot to the failed system and installing the correct package.