Rev Lucius Debataradja Mamora was a Batak, a Methodist missionary from Sumatra. He was educated in a Methodist school in Sumatra and Methodist Teachers' Training School in Batavia. After his graduation in 1926, he served as a teacher and preacher for a number of years before he was invited by Bishop Edwin F. Lee to work among the Sarawak Dayaks at Kapit in 1939.

In June 1939, Mamora travelled with Rev Paul Schmucker, an American, to visit the Ibans in the upper Rejang River. Rev Schmucker had obtained permission from the Resident in Sibu, because at that time westerners couldn't travel upriver, only to Kapit.

There was fear they would have their heads taken. That didn't hold for Rev Mamora, he could go anywhere.

After travelling for one and half day, they arrived Kapit at about 1 pm. That's where they met Penghulu Jugah (later known as Tun Jugah), Gerinang, Sibat. They spent one night in Kapit, and the next day they rented a five-horsepower motor and a 36-foot boat from a Malay.

“We took food, everything we would need. In the boat were me, Schmucker, Penghulu Gerinang, Penghulu Sibat, and Temenggong Jugah. Because the boat was long and the motor small, it took us a day-and-a-half to reach Temmenggong Jugah's longhouse. First, we spent a night at Temenggong Koh's house. That was the first time I had been to a longhouse, the first time I had seen skulls (antu pala). The people told me that the skulls would spit on guests on their first visit. So that night, when everyone else stayed in the family, rooms, I stayed on the verandah because I wanted to see the skulls spit at me. I stayed awake the whole night, and not one skull spit at me!”

The next morning, Mamora and the party travelled downriver to the house of the late Tun Jugah. That night, Jugah's daughter, Munan, became critically ill. She was taken to Kapit, where she died. Mamora and Schmucker discussed their alternatives, and they agreed that they should return to Sibu. The child's death and the family's grief made a return inappropriate. That visit was the only one they were to make together to the Baleh.

Mamora and Schmucker started a small mission school for the boys in Pantu, near Kapit later. After two years (1941), Schmucker went back to the United States on leave, and before he returned to Sarawak, the state was occupied by the Japanese.

However, Mamora stayed on in Kapit farming and working with the Chinese Methodist church. The work among Iban suffered a setback. The mission station was abandoned when the Japanese took over Pantu as their base. Throughout the Japanese Occupation, Mamora retained his friendship with Jugah, Sibat, and Jinggut, and other Ibans. From time to time, they provided him with rice and coconut oil, both in short supply.

To avoid being seized by the Japanese, Rev Mamora and his family fled and took shelter at the Iban longhouse of Sungai Majau, a tributary of the Balleh River, for a period of two years. The headman of the longhouse was Nuing's father. Mamora used to plant rice to support his family. After the Japanese occupation, the Ibans at this area were baptised to become the first Methodist Iban Christians.

One day, near the end of the Japanese Occupation, the Union Jets were attacking Kapit through air strikes. The Chinese and Mamora were all hiding at Ka Ong Methodist Church, at Selirik, afraid to step out.

The day after the strafing, a Chinese suddenly shouted that there were eight Ibans outside. They grabbed hoes and spears, all 30 of them, ready to fight. Mamora looked out carefully and found that they were not enemies but Nuing, his friend, bringing rice for him. Nuing had gone to find him at Pantu. Mamora was not there, so they came here to find him.

After the Japanese surrendered, more Indonesian missionaries were sent to assist in the mission work at Kapit. Jaleb Manurung and Philemon Sirait (Mamora's fellow Batak colleagues) were among them. Mamora stayed in Sibu after he retired. He later moved to Kuching. His first wife, Elizabeth, died in 1947 and was buried in Singapore.

Perhaps the most significant and enduring of Mamora's contributions was his translation of more than 100 hymns into Iban, and his editing of the Bup Sembayang Iban (worship handbook). He also taught in Methodist Theology School in Sibu for the Iban Section during the 1960's. His second wife was Yiomina, and he had seven children: Ida, Borney, Saroha, Satia, Daulat, Tolman, Tracey and Sarina.