The Keep:Mage Guide

Overview
As of this writing, the Mage may be the "best" character in Habitica. This is admittedly highly subjective, but to give a little backing to the statement, the Mage: That being said, as always, the "best" character is relatively to how you play the game. The Mage works best for players who want to advance quickly and are good at staying on top of their habits.
 * Levels the fastest of all classes
 * Does the second most damage to bosses
 * The only class with 4 potentially useful skills

Stats
Allocating stats for the Mage is extremely simple: pour 100% of your points into Intelligence. Not only is Intelligence the basis for the damage dealt by your primary skill (Burst of Flames), but it also significantly increases your mana and the rate at which you level up.

The other 3 stats will reach sufficient level from equipment, levels, perfect days and other buffs.

Equipment
As mentioned above, the only real stat requirement for the Mage is intelligence. As such, your final gear should be: The first two of these pieces can be obtained by level 15 or so. While waiting on the Nobel Tunic, the standard Royal Magnus Robe (your highest class-specific armor piece) will do just fine.
 * Nameless Helm
 * Golden Staff
 * Nobel Tunic

The only exception would be when you are involved in a collection quest, in which case using Perception boosting gear is a good choice. The two legendary hand weapons, for example, are good choices here.

Skills
In small parties and when questing solo, Burst of Flame is truly the only skill you'll need. This is your bread and butter. It deals 10th of your Intelligence in damage, rounded up. So if you have 121 Intelligence, it will deal 13 damage. The amount of experience you get is based off of a combination of your Perception points and the value of the task you use it on. Always use it on a task with a very high task value (very blue Habit or a Daily with a long streak).

Ethereal Surge and Earthquake are both useful in large parties. When you have 2+ other characters who are strong damage dealers, you can often kill bosses more quickly by giving them mana than by dealing damage yourself. You can also boost the mana of Rogues on your team during collection quests so they can dramatically boost the Perception of your party.

Because most of the gold you'll recieve will come from long streaks, it's worth preserving them with Chilling Frost as long as you don't have to do so too often.

Keep in mind, however, that the more you use Burst of Flames vs your other skills, the higher level you'll be and the more you'll be able to help out.

Boss Fights
As mentioned, the Mage is second only to the Warrior in his ability to deal damage to bosses. A level 100 Mage with a "Perfect Day" bonus can deal around 1500 damage to a boss in a single day.

Simply use Burst of Flames as many times as possible, especially when you have the "Perfect Day" bonus or other buffs.

If you have several other Mages or Warrior on you team, it may make sense to buff them instead, however.

For collection quests, strap on Perception boosting gear and buff the mana of Rogues in your party so they can use Tools of the Trade.