Rusty spikes

Rusty spikes are used during Carnillean Rising when preparing Philipe's quest. They are used in the construction of two different possible features in the quest cave:
 * Spike pit in the obstacle hotspot - 15 spikes required along with 2 bone scraps.
 * Impaled skulls in the wall decoration hotspot - 3 spikes required along with 4 animal skulls.