Ryder's known history is limited; he and Dr. Vargas are old friends, going way back as he knew Charlotte and his now deceased sister (Lucas' mother) had arguments with the Doctor in the past.
When Lucas's parents passed away years ago, he became Lucas's guardian. His line of work does have him travelling a lot, so he regularly leaves Lucas in Dr. Vargas's care as his lab assistant. Sometimes he'll have Lucas come along on his trips, but other times, if for his safety to stay behind. Ryder, other than Lucas acts as a voice of reason to Dr. Vargas when he sees his friend being about to do something foolish or wrong.
Ryder is knowledgable about Goblins by unknown means, but it helps his group in the expedition to find out how and where they been getting their advance arsenal from their leader, Gundahar. He devised the plan to having fake relic beacons made to be picked up during a Goblin raid to track down the location of Gundahar's weapons factory. He also helped the doctor in finding the location of the real key to the locked doorway of the giant relics. After Knack defeats Katrina and she falls onto one of the stone platforms over lava at Obelisk Mountain, he stayed behind to save her as the Doctor, Lucas and Knack goes after Viktor for the key.
Ryder was supposedly believed at first that he might've died during Mount Obelisk's eruption, but in the ending sequence, it was later revealed that he survived and was carrying Katrina across an unknown desert.
Ryder is voiced by Travis Willingham, who voices Knuckles the Echidna from the Sonic the Hedgehog series as well as the anime Sonic X, voiced Reggie Rowe and Shane in InFamous Second Son and First Light respectively as well as voiced Rex in Murdered Soul Suspect.