Halldor is an Icelandic black belt under Gunnar Nelson. He is a multiple Icelandic national champion and active competitor in Brazilian Jiu Jitsu all over the world. Halldor currently holds three titles on prestigious grappling shows.
Halldor is the Head Instructor for kids and teenagers at Mjolnir MMA.
Halldor has been globetrotting since 2012, currently he has attended fourteen camps and taught at four of them.