Oisin
Oisin is the eponymous hero of this epic poem, and his "wanderings" take place primarily in the otherworldly realm, in the Immortal Islands. He seems to have been a warrior, or soldier, of some description, and also a poet, because it it through his poetry that Niamh, a fairy princess, falls in love with him. She seems to bewitch him. When he agrees to leave with her for the islands she enables him to become immortal with her, but he still retains the characteristics that he had in the human world.
For this reason he is also adept at carrying out battles in the Immortal Islands. The main battle is with a demon, and it is not an easy victory for Oisin. The battle takes a century but he comes out on top in the end. This mirrors his courage and tenacity in his former worldly life.
Despite the pleasures of the otherworldly realm, and the fact that he is still a youthful man at the age of three hundred, Oisin, a patriotic man who loves Ireland, is still essentially very homesick. He particularly misses his old comrades and wants to return home to see them. Unfortunately he forgets that they have not enjoyed the luxury of immortality and are consequently long dead when he arrives back in his former home. He finds much changed and feels like a fish out of water. Whilst riding Niamh's horse, he also has what seem like superpowers; he is able to lift with one hand a sack of sand that two men together are struggling with. However, he falls to the floor when his saddle breaks and finds himself a three hundred year old man at the end of the poem.
Niamh
Niamh is a fairy princess and like many fairy princesses completely determined to get her own way. She has fallen in love with Oisin through his poems and wants him to spend the rest of time with her. This is something that she can offer because she has the ability to take him to the Immortal Islands, where he will never die. They travel the islands together, and enjoy immortal life in a setting that seems entirely other-worldly. Niamh genuinely loves Oisin despite bewitching him, and when he yearns to revisit his home she lends him her magical horse so that his return to the Immortal Islands, and to her, is guaranteed. She warns him not to touch the ground because her powers do not extend that far.
The Stolen Child
The boy in this poem does not have a name. He is the object of the fairy's desire and he is to be whisked away to their world without his knowledge. He is a boy who loves his home and who will undoubtedly miss everything that is familiar to him. From the descriptive verse he appears to be a happy child, who is loved by his family and who comes from a happy home.
The Faery Speaker
She seems to speak for the faeries as a group, explaining what their intentions for the little boy are, and warning that they are going to take him to their world. She admits that it is different from the world he comes from and that the transition will be difficult. Although the Speaker wants to frame their actions positively, as though they are doing something good and generous for the boy, she also makes it plain that they are stealing the boy because they want to and because they can.
The Speaker, "Down by the Salley Gardens"
The Speaker in this poem is rather melancholy. He is looking back at his life so far, probably because he is lonely. He realizes that this loneliness could easily have been avoided had he taken his love's offer of romance and love when it was given. He did not act appropriately, which he puts down to his youth and inexperience, and consequently has been without love ever since.
The Lost Love
There is not much known about the Speaker's lost love, except that she is from a relatively well to do family; her feet are described as "snow white" which tells us that she is not often outside or performing outdoor tasks. This was possible only for the better-off households. She also seems to have been the more forward of the two at the start of their dalliance.
