Spell points

Spell points (or SP) is a person's capability to perform their more enhanced skill sets. Performing these tasks can be mentally exhausting, and a person's SP represents how mentally fatigued they are after executing any skill.

You can check your current HP, SP, and EP by typing hp in game.

Uses
There are numerous mentally exhausting tasks in Threshold that would leave even the most rested psion feeling like their brain is turning to mush. A short list of commands that require SP, aside from guild related skills are:
 * tells
 * speaking racially
 * checking your friendship band/personal score
 * some party commands