Okay, that last post was from my mobile. But I'm in front of a keyboard now, so here is what you should probably know about Howland Reed by now. Howland is the head of House Reed and a banner-man to the Starks. His lands are the southern-most part of The North where it meets the Riverlands at a place called "The Neck". This area is swampy marshland filled with "lizard-lions", which sound like some form of crocodilian species. Howland and his people are known as Crannogmen because they live on "crannogs", floating islands made of reeds that can be moved deeper into the swamps when they don't want to be found. Crannogmen are generally small, reclusive people who are primitive by the standards of the Seven Kingdoms. They are expert hunters and rely on guerrilla warfare when The Neck is attacked. They usually fight in leather, rather than steel and wield frog-spears knives made of bronze. They do not have maesters, septons or knights. Crannogmen seem linked to nature much more than the other people of Westeros. They have a friendly history with the Children of the Forest still believe in things like greensight (Bran's visions) and wargs. When his son Jojen had visions telling of Bran's future, Howland sent Jojen and Meera to Winterfell under the pretense of pledging House Reed to the service of Robb Stark as King in the North. Neither Howland Reed, nor his home of Greywater Watch have been seen since the start of the War of the Five Kings.
As Jojen explained to Bran during their journey north of the wall, Howland Reed became close friends with Ned Stark at the infamous "Tourney at Harrenhal". He was being bullied by a group of squires when Ned's sister Lyanna Stark stepped in and put them in their place. Later, a mysterious, small-statured knight (that many suspect was Lyanna) entered the tournament to fight for Reed's honour and won several jousts before disappearing. This was the tourney that ended with Prince Rhaegar Targaryan defeating Ser Barriston Selmy to become champion. Instead of giving the wreath of blue "winter roses" to his wife Elia Martell, Rhaegar rode right past her to where Lyanna Stark was seated and crowned her the tourney's "Queen of Love and Beauty" instead, causing a huge scandal. Rhaegar already had a wife and Lyanna was already betrothed to Robert Baratheon. Ser Barristan explained to Danaerys (last season I think) that he still believes that if he had only won that tournament and chosen his own love-interest to honour, then Rhaegar might not have later abducted Lyanna and Robert's Rebellion and the downfall of House Targaryan could have been avoided.
During Robert's Rebellion, Howland Reed fought alongside Ned Stark and became his most trusted friend. He was one of the men that Ned took with him to the Tower of Joy on the Dornish border to find Lyanna after the fall of King's Landing. The tower was defended by three members of the Kingsguard, including the legendary Ser Arthur Dayne, the "Sword of the Morning". Howland saved Ned from being killed by Dayne, leaving Ned and himself as the only combatants to survive the fight. He is the only person left alive who knows what happened when Ned went into the Tower of Joy after the fight.