World of Warcraft: Apexis Crystal Bonus Event until October 13
During the Sign of Apexis bonus event, you'll gain bonus Apexis Crystals from eligible creatures.
Furthermore, completing the this-bonus event-only quest "A Time to Strike" awards a sizable amount of Oil to fuel your Naval Missions, in addition to a big pile of Apexis Crystals.
The point of picking up lots and lots of extra Apexis Crystals is, of course, to spend them! Here are some of the possibilities.
For most players, spending Apexis Crystals on gear upgrades is a great way to improve your overall item level. There's something for every slot at item level 650, so if you've still got a low-level item in one or two slots, you're covered. Visit Ravenspeaker Thelnaas in Tanaan Jungle to buy armor for 5,000 Crystals apiece, a weapon for 10,000 Crystals, and Empowered Apexis Fragments for 20,000 Crystals. Empowered Apexis Fragments are Battle.net Account-bound, and upgrade your Baleful gear from ilvl 650 to ilvl 695.
Some nice new collectibles came along with Tanaan Jungle. You'll want to consider:
Reins of the Corrupted Dreadwing mount (150,000 Apexis Crystals)
Rukhmar's Sacred Memory toy (50,000 Apexis Crystals)
Blazin Firehawk pet (2,000 Apexis Crystals)
Solar Priest Vayx follower (1,000 Apexis Crystals)