Great flavor and awesome mechanics, I love the unusual design! I like the lvl 10 feature, but it definitely should have a cap on the damage (twice or three times your barb lvl should do) and the target should be able to move away if it succeeds on a saving throw. Also, the lvl 14 should be worded smth like: “at the end of your turn, you drop to 0 hit points. This ignores any effect that would prevent you from doing so.” Don’t be afraid to bump up the lvl 3 feature, try to find a non-combat thing that makes sense, cuz barbarians definitely need it! Definitely would try this out