Scuba's directions for spawning Martar have been confirmed to function circa 2016:
Spawning Marter Icebear is easy if you have a tracker and a wee bit of patience.
Since Marter and Karg Icebear are so interrelated, I will be posting this under both of their names on Zam
Marter Icebear and Karg Icebear are relatively easy to spawn but a good tracker is required. These two are not on the same spawn cycle, though both of their cycles do include the same mobs.
The starting area is between the Wayfarers Camp and the west branch of the river above the split. slaughter any roaming mobs in that general vicinity. Mobs not included in the cycle are adult mammoths. What you are trying to spawn are polar bears, polar bear cubs and any of the Icy Goblins. These can spawn in any of about 20+ spawn sites. Generally, they will spawn between the ice giant fort and Megan's Tower, from almost to the north LDoN entrance to the lower LDoN entrance. The PH for these two re-spawns in 12 seconds +/- 3 seconds. Once you have a PH on tracking, stop the slaughter and wait about 20 seconds to make sure the slaughter re-spawns are done. Kill the PH and watch for what spawns about 12 seconds later. The re-spawns will include spiders, orcs and mammoth calves. Keep track of any other mobs that spawn at the same time, Tundra Jack and Iceberg will be killing at the same time. Almost every mob in that area of the zone re-spawn on the same time frame. Keep killing the re-spawns until you get either Marter or Karg. If you are after Marter and Karg is up, leave him up and repeat the killing of PHs until you get the Icy Goblin or the polar bears. These will become your new killing cycle.
Notes of interest: 1. I have had Marter spawn 12 times in a row then again not for over 25 kills of the PHs.
2. Normally, the named and the PHs will spawn in the north half of the zone, but they can spawn in the south..
3. I used a bard to track the re-spawns so that I would not get the spawns from the kills in the canyon area on tracking.
4. Watch the tracking very closely as the cycle contains orcs that can and will spawn all over the zone.. I:E a Snow Orc Trooper or Shaman. It also contains Snow leopards.
5. The Tainted Mammoth is not part of the cycle nor are any of the skeletons.
Good luck and good hunting.