The mastery primers are currently only available on: Atlantic. On Atlantic shard we have every primer you would need ready for delivery. These items are consumed one time only use to unlock level 3 mastery bonus for 1 skill. These items are shard bound which means you can not take them to other shards unless you consume it and then transfer your character. Each primer unlocks a different set of abilities based on the skill you choose to activate. The most desired masteries primer is the animal taming one.