To get Brennalfar Amber in Tribes of Midgard, you will need to locate Brennalfar warriors and Archers in the Smokey Highlands region and kill them.
Killing both Brennalfar enemy variants will drop the resource upon death; however, it may only do it depending on the power level scale or if there is a big camp nearby.
Because of that, we highly recommend raising your power level by upgrading your armor/weapons and leveling up in the game.
You can do both by gathering souls by farming resources and clearing camps, and then putting it towards upgrading both the Blacksmith and Armorsmith.
Farming camps will also help you level up, which will, in turn, raise your power level by a small amount. When you reach a power level of at least 150 to 200, you should be safe to roam some of the stronger Smokey Highland regions.
But don't forget to pack some heat resistance potions or make armor with high heat resistance. Doing so will allow you to explore the Smokey Highlands without taking heat damage.
That said when you reach the Smokey Highlands, target camps, and you should find Brennalfar enemies to farm - use cold weapons if you want to gain an advantage over them.
Alternatively, if you are having trouble locating them, you can always try finding a Sorrcer as they will sell the ambers if they are located in the Smokey Highlands.
Check out some more Tribes of Midgard guides at Pro Game Guides!