The English text says that you get 3 stacks, "each stack reducing damage taken by 10% and nullifying all action direction requirements". This means that when you first use it, you have -30% damage taken. After you use one weaponskill it goes down to -20%. After the second weaponskill, -10%. The protection wears off with the third weapon skill. If you don't use three weaponskills before the 10s pass, you forfeit the remaining stacks of TrueNorth-ish.
Unrelated to its effect, it has 3 maximum charges that recharge one per 30s.