Remember, you must join the Legion by talking to General Darius in Gnisis. Once you have joined, you can get quests from the other Legion commanders. You'll find Imsin in the Buckmoth Legion Fort (south of Ald'ruhn) on the lower floor. She can handle your rank advancements up to Rank 8 (Knight Protector), but will refer you to Ebonheart once you are ready for Rank 9 (Knight of the Garland).
Horror of horrors! People in Ald'ruhn are engaged in smuggling. Specifically, Drinar Varyon. If you are a member of House Hlaalu, you may have even helped him. But it's not the ebony that we're concerned about this time. Your interest is in his smuggling of Dwemer artifacts. So hop on over to his house (he's across the street from the Ald Skar Inn). Just about anyone in town can direct you to him.
Once you are in his house, you need to find the evidence. The chests look awfully inviting, but all you'll find in them is Ebony and provoke a fight on top of it. Instead, look among his clay pots (there are a lot of them, so you'll have to look closely) for a Dwemer Tube. Take it and report back to Imsin for your reward: 5 faction rep points and 10 disposition points. What? You thought that you were actually going to get paid for this stuff?
Joncis Dalomax, a Knight of the Order of Ebonheart, is being held prisoner in a Daedric ruin called, Ashurnibibi. The ruin is a short distance northwest of Hla Oad. The entrance to the shrine is more or less in the middle of the ruins and faces west. You'll find the usual complement of Daedric critters wandering around.
Inside the shrine itself are a couple of Orcs that need a lesson about holding knights against their will, but no other critters unless you generate a Dremora by pilfering the shrine offerings. Dalomax is in the chamber behind the shrine. Report back to Imsin after releasing him for more Imperial Legion rewards: 5 points of faction rep and a 15-point disposition boost.
Varona Nelas, a Telvanni outcast, is blackmailing a Buouyant Armiger. You need to recover the glove that is evidence of a love affair from her in Assumanu, a cave in the Sheogorath region (not to be confused with Assemanu, a 6th House base in the Bitter Coast region). You are told that Assumanu is south of Ald Redaynia, which will be marked on your map. Once again, you got cruddy directions. If you were to draw a line going northwest from the Valenvaryon stronghold and another line going northeast from the Urshilaku Ashlander camp, they would intersect just about at Assumanu's front door.
When you go in, turn right to get to Nelas (left will take you to a couple of sorceresses, who will not be happy to see you). On the other side of a leveled atronach, you'll run into Allimir, a Bosmer, who will tell you that you don't have an appointment. You do not need to fight Allimir (nor should you unless you want to fight Nelas, too), just find a way around him. Jump, Levitate, Sneak, whatever. You also do not need to fight Nelas. If you can get her disposition up to 70 or more (bribery or some other Persuasion will work), she'll give you the glove and send you on your way.
Return to Imsin for some more lovely Imperial Legion rewards: 5 points of faction rep and a 10-point disposition boost. The glove, by the way, belongs to Ilmeni Dren in Vivec (Canal South One) and you can return the glove to her. There is no difference in the reward, just an additional journal entry. Killing Nelas will also generate a different journal entry, but will not change the reward.