Ralpachan was a monk at Det-Sen Monastery. He helped the Second Doctor fight the Great Intelligence's robot Yeti.
Ralpachan was a guard at the monastery. When Khrisong tied the Doctor to the gate, he ordered Ralpachan to act as a lookout and tell him if he spotted any Yeti heading towards the monastery to rescue the Doctor. He spotted what he thought was three Yeti, but was really Jamie McCrimmon, Victoria Waterfield and Edward Travers.
He saw Travers leave the monastery against orders but let him go because Travers said he had Khrisong's permission. He was guarding the gate when a possessed Songsten left. Songsten hypnotised Ralpachan into forgetting that he had seen him.
When Victoria was imprisoned with Thonmi, Ralpachan brought them food. Victoria pretended the water made her sick and escaped when Ralpachan went to get more water for her. When the other monks left the monastery, Ralpachan accompanied Travers to the cave to try to destroy the pyramid inside, but their mission failed. They returned to the monastery and were forced to wait as it was guarded by three Yeti. When the Yeti headed inside the monastery, Ralpachan and Travers followed, arriving at the inner sanctum just as the Intelligence was defeated and Padmasambhava died. (TV: The Abominable Snowmen)