A unit where the majority of the models have this rule can declare to use Counter-Charge as a charge reaction (including Frenzied units) if they are charged to the front by an enemy that is more than its M value away from the Norse unit.
Before the enemy roll their charge distance, the Norse unit must take a LD test. If failed, treat the charge reaction as a Hold. If passed, the Norse unit moves 2D3" forwards using Random Movement, but stopping within 1" of any enemy unit. They may also use any Quick to Fire weapons they might have before they move.
The enemy unit then rolls their charge distance and complete the charge as normal. If the charge is successful, then both units will count as charging in the ensuing combat phase.