Although the raids are more action-type, everything around it, it is all roleplay. You as a group have to decide how strategically build alliances or make enemies, or set your group more like switzerland (neutral). It is a political roleplay. The crystal is the source of power, and how you wish to protect it is up to the whole group. I strongly suggest the clans to work together. You can even ask your allies to protect it for you too. It is all up to you.
Also, when you decide your alliances, you can also promise other groups stuff that they might find valuable against protection (shields?), or slaves, or other goods.
You can pay for protection other groups as well. In that case, the other group will initiate the raid from their camp, but when it is time to deliver, they will deliver the crystal to your camp.
These are just random ideas, but you can make up other ideas of deals and group strategies.