Zed's Jagged Knife

In Gangplank's updated lore, he raided the Temple of the Jagged Knife, and this act enraged Zed. So what is the knife's importance? Is it one of Zed's combat weapons, or was it just a piece of valuable, ceremonial loot? The knife was coloured crimson and it has an exquisite design. The knife also showed up in the Burning Tides story.