Jason Momoa -- Scaring Everybody With Maori War Dance

Jason Momoa's character was killed off "Game of Thrones" WAY before it became trendy ... but he's keeping up with one CRAZY-INTENSE cultural tradition that would make even a Dothraki warlord quake in his sandals.

Check out Khal Drogo (middle) doing the "Haka" -- the traditional ancestral war dance of the indigenous Māori people -- at the beach in Auckland, New Zealand on Sunday.

Momoa hails from Hawaii but says he's obsessed with Polynesian culture ... he even did the Haka dance -- in character -- as part of his GoT audition.

Momoa's no hack at the Haka ... but if you want to see something REALLY scary, check out the New Zealand national rugby union team -- which performs the dance to scare the crap out of opponents before matches.

Not pictured: whatever's running down the other team's legs.