Arcane Refreshment is a mage-only quest that teaches Conjure Water (Rank 7). With the release of the Burning Crusade expansion, the quest is largely obsolete, now that this spell rank can be purchased at a trainer.
You will need:
Head into Dire Maul North (armed with your Crescent Key or accompanied by a rogue). In front of you there is a ramp leading down into a pit-like arena filled with hyenas. Also in front of you is an ogre. Wait for a while and he'll move off to your right, leaving the ramp clear. Run down the ramp until you can jump onto the left "wall". Hug the wall to avoid aggro (note that the dogs here can see through stealth) and slip down the leftmost ramp to another locked door. Open it (using the key or lockpicking) and follow the path to The Athenaeum. Talk to Lorekeeper Lydros and acquire the Arcane Refreshment quest.
Now, head back into Dire Maul East with a full group. You may be able to save some time by jumping down into the courtyard if you can survive the falling damage, and avoid the mobs below. Hydrospawn is in a room down a corridor at the southeastern corner of the courtyard. Kill him and get your Hydrospawn essence.
Finally, return to the The Athenaeum and turn in the quest.
A <race> mage! How wonderous. I have not seen one of your kind for... oh what is it going on now? 500 years!
I have something that will quench your thirst, but first you must do a task for me.
There is an anomaly in Eldre'Thalas. A water elemental has taken residence in the east wing. His presence must be catalogued!
Venture to the Warpwood Quarter and extract a portion of the elemental essence of the Hydrospawn. Return it to me and I shall teach you a useful cantrip.
Yes? Do I know you?
Wonderful! Who are you again? Oh it matters not. What was I supposed to give you? Hrm... well you are a mage, perhaps you will find this useful.
Upon completion the mage will learn a new ability: Conjure Water (Rank 7).
Patch 1.3.0 (07-Mar-2005): Added.