Need help with a hook

There are a few ways you can approach the situation:

1. An orcish worg-rider (or a whole band of them) carrying the invitation to a clan meeting is in a hurry to deliver the message, along with a generous gift of coin. This scenario can start with the PCs stumbling upon a gold coin lying on a set of worg tracks. If they choose to follow the tracks, they will find a gold coin every half a mile (increase or decrease frequency as needed), until they find the worg-riders setting up a camp in the woods. If the PCs are greedy and attack the orcs for the coin, they will also find the message that includes the time and place of the meeting on the orcish messenger(s). If they are stealthy about it, they can also steal the sack of coin along with the message. Or, they can follow the orcs from a distance and watch the messengers deliver the message and the gift to a sizable orc clan.

You may replace the coin with items of magical power, gems or things of similar value.

2. The party stumbles upon a freshly devastated village or town, with all of its inhabitants either brutally murdered or missing. The dead are all boys, men and older women. It's pretty easy to find out that orcs are kidnapping fertile women for pleasure and reproduction, and it only gets worse over time. You can make this hook tied to a PC's background, where they return home to find it in ruins, or that they find out that a family member, a likable NPC or a potential romantic interest has been recently taken by orcs.

Prod the PCs where it hurts to get their attention. It usually works!

3. The Warchief is not shy about displaying his power. If an orc clan doesn't accept his invitation, he kills them with his voodoo magics and sacrifices their children to his demonic friends via gruesome rituals. The PCs can stumble upon a devastated orc clan and find a survivor who tells them of the Warchief's warlock treachery Heck, you could tie this one to the ones above, if you want.