Earl
Overview
An earl is the leader of a Dawnish noble house. The title is used for both men and women. Each noble house appoints an earl, to lead the house. Being the earl is an inherently political position; the character is not expected to undertake the kind of glorious actions appropriate for a Dawnish noble - instead their time and energies should be devoted to ensuring that the other members of their house have every possible help to act. In this way the glory of the house is ensured and it is this glory that reflects in turn upon the earl themselves.
Setting Tests
One of the most important roles of the earl is setting Tests of Mettle, Ardour and Resolve. This ability underpins most of the power of an earl, and allows the Dawnish system of noble houses to operate. Make sure that you understand the tests and how they work, they can be a very powerful tool in helping you control your house as well as making awesome stories!
The key thing to appreciate about the tests of Mettle and the test of Ardour is that they have absolutely no value at all, except what you give them as earl. While the setting claims that everyone who is a noble has passed their Test of Mettle, the reality is that any player who wants to play a noble can just create a character that is already noble. That means that anyone who has deliberately created an adult character that is trying to pass the Test of Mettle has done so precisely because they want the challenge of a near-impossible test, they want the drama and the epic story that comes from passing such a test.
You won't do these players any favours at all if you set them an easy test. More likely you risk harming their fun by removing any sense of challenge and development for them. If you're called upon to set a Test of Mettle, don't be rushed into it. Passing a test should take years, so it's fine if it takes you a day or two to come up with something cool. If you are struggling to think of something cool try talking to the Dawnish Egregore or to the other earls.
Spend some time talking to the character and try to get to know them and understand them. The more appropriate the test is for that character, the better. You want to set a test that is difficult, but you want it to match their character's skills. Telling a magician that they have to duel ten orcs armed only with a spear is difficult to the point of impossible - but it's no fun for the player. Telling them they have to retrieve the Eternal Queen of Summer's crown and bring it to the lake of ice is probably more difficult - but it's something they won't be prevented from doing because of their character's skills.
The only exception to this is with young players who have come of age in-character. These players have not had the chance to create a noble character, as all Dawnish children begin as yeomen. It is possible that they will be excited by the chance to spend years trying to become noble - but it is possible that they will want to play a noble character without this barrier. In this case it may be appropriate to set an easier test or even have one conducted "between events" if the player wishes. Talk to the players involved, there are no hard and fast rules for this sort of thing, it is down to the individuals and how they feel about it.
Some noble houses use traditional, publicly known tests. For example, House DuPont of Astolat traditionally demanded the head of an orc shaman or warlord, taken in battle. If your group has decided to create a traditional test for the house then you can choose to use that in play whenever you are asked to set a test.
Enchanters
An earl who possesses magical powers may style themselves an enchanter. With the resources of an entire noble house to back them up, Enchanters can exert a great deal of influence over the nation. Sometimes an earl becomes an enchanter later in life, studying magic as a means to expand their personal power.
Most enchanters possess at least a basic mastery of ritual magic, focusing on the magic of the Summer Realm (which grants strength to them and their troops) and the Autumn Realm (which deals with prosperity and influence). The primary weakness of ritual magic from the point of view of an enchanter is that it is most powerful when supported by a group of ritual magicians, and Dawnish noble houses tend to shy away from this practice in favour of the more glorious battlefield incantations.
Perhaps most importantly, an enchanter is in a good position to deal with the Eternals on a more-or-less equal footing. Enchanters often pursue relationships with Summer Eternals, who respect the personal power of a mighty individual more than they do the more diffuse power of a ritual group or lesser magician.