Protector Casdin

Protector Henry Casdin is the leader of the Brotherhood of Steel Outcasts in the Capital Wasteland. According to Elder Owyn Lyons, he was one of the best fighters in the Capital Wasteland Brotherhood of Steel before he took other Brotherhood members and formed the Outcasts in order to continue the original mission. He trades the Lone Wanderer for technology that is acquired across the Wasteland and in return gives out useful supplies that the Outcasts' possess in abundance (see Technology scavenging below).

If you bring him any Outcast Power Armor or Outcast Power Helmets, he will take them from you without giving anything in exchange. However, he won't take away Linden's Outcast Power Armor if you have it with you when you talk to him.

Protector Casdin can be found standing at the entrance to Fort Independence, the Brotherhood Outcasts headquarters. He holds the key to Fort Independence. The player can unlock the side quest of scavenging for technology by first speaking with Defender Morgan.

Technology scavenging
You can trade power armor (except for Tesla Helmets, the T-51b Power Armor and helmet, the Prototype Medic Power Armor], Brotherhood Power Armor and helmets, Lyons' Pride Power Armor, and Outcast Power Armor and helmets), any type of energy weapon (except for unique weapons, Laser Pistols, and Gatling Lasers), sensor modules, and scrap metal. In return he'll give you either of these, in accordance with the perceived value of the item: Condition does not appear to matter when trading scavenged technology.
 * 5.56mm ammunition
 * Frag grenades
 * Rad Away
 * Stimpaks

If you speak with Protector Casdin while carrying or wearing Outcast Power Armor, then he takes it from you without recompense. It does not appear to be possible to prevent this. The one exception to this rule is the quest reward item Linden's Outcast Power Armor.

Its worth noting that you can get a stimpak for less scrap metal here than you can at the other trade in sites.

Technology Scavenging Value Table
† Scrap Metal must be traded in groups of two.

Trivia

 * Should the player give Casdin a Enclave Power Armor, Enclave Power Helmet, or Tesla Power Armor, Casdin will wear them. He would wear the Tesla Power Armor more than the Enclave Power Armor and he would wear the Enclave Power Armor and Helmet more than his own Outcast Power Armor. This can be rectified by using console commands to have him equip his Outcast Armor back.

Bugs

 * There is no option to give him a Tesla Power Helmet
 * You also can't give him a Gatling Laser, though this may be due to it's classification as a big gun