I was curious about what the tusk is even used for

https://oceanconservancy.org/blog/2019/03/08/exactly-narwhal-tusk/

There’s research that suggests the narwhal tusk is used primarily for hunting, but contrary to what you might be imagining, they don’t actually spear their food. In fact, there’s video evidence indicating that they instead give a quick and firm “tusk tap” to momentarily stun their prey (usually fish, shrimp or squid) and then quickly suck them up.

TIL that narwhal tusks are for smacking and not stabbing

The video link, although I haven't watched it myself and didn't find the timestamp: https://m.youtube.com/watch?v=OoTjLIN67Bw