New hotfixes have been pushed to Halls of Valor which includes a new speed boost buff that seems like it will apply when you kill Hyrja or Fenryr.
New Speed Boost in Halls of Valor
In the latest set of hotfixes, a new speed boost buff has applied which looks similar to the current speed boost in Halls of Valor. The current speed boost is Odyn’s Blessing which is a 150% movement speed buff and gives you access to the final two bosses.