If a bow, dagger, magic, or staff foe initiates combat
One origin of Kriemhild may be the figure of Norse Mythology (Also referred to as Gudrun), an important character from the epic Nibelungenlied. Alternately, it could come from the words for "mask" and "battle" in German.
If hacked in to give to a unit, Phantasm is active even if said unit cannot wield Kriemhild. In addition, it also isn't weapon locked despite being enemy-only.