The spear Gáe Bulg is one of those mythical items where its reputation almost overshadows the actual owner, which is saying something when that owner is Cú Chulainn. I've always read its power as a layered thing. On a surface level, it's a physically unstoppable weapon—once thrown, it fills the battlefield with barbs, making a single wound into a fatal, unfixable mess. That's raw, destructive power anyone can understand.
But the symbolism gets more interesting when you look at its origins and rules. It came from the sea, crafted from a sea-monster's bone by a female warrior, Scáthach. That ties its power to the Otherworld, to a liminal space between elements, and to feminine martial knowledge, which adds a complex, almost otherworldly legitimacy to it. Then there's the geis, the taboo: Cú Chulainn could only use it in direst need and couldn't refuse a duel to the death afterward. The spear's power isn't free; it's a last-resort tool that comes with a death sentence for the user, binding its destructive force to concepts of honor, fate, and tragic inevitability. Its power is as much a curse as a blessing, which feels very true to the Celtic heroic cycles.