The most popular folk tale of the Borok people relating to ‘twi’ or water is about two sisters –  

Raima and Saima. The story goes like this:

The father of Raima and Saima was an ochai kotor or chief priest, who performed rites and rituals for the welfare of the villagers, and was always busy drinking and merrymaking. He did not have time to think for the family, and the mother also followed the father. The two sisters were left by themselves most of the time. The family was dependent on huk or shifting cultivation, and as the parents did not have time, it was the two sisters who were involved in the cultivation. In such cultivation, construction of a garing or temporary hut was essential to protect them from rain and sun, and for taking rest when needed. Both the sisters time and again told their father to build a garing for them at the huk land but to no avail. One day, while the two sisters were in the huk land, there was a sudden storm and as both the sisters did not have a garing they were left unprotected. In such a situation the elder sister Raima out of deep sorrow and anguish made a vow to marry anybody or any creature whoever would build a garing for them. 

A python heard Raima’s vow and immediately built a garing for the two sisters. Raima and Saima also came to know about the python, but interestingly only Saima who could see the python as python, but in the eyes of Raima, the python was a handsome young man. Raima immediately fell in love with the python. Whenever the two sisters started early in the morning for the huk land, they usually carried their lunch with them. The python ate the lunch meant for the two sisters and the sisters shared the little that was left over. The sisters became thin and unhealthy, as they were deprived of a proper lunch. 

One day the father asked Saima as to why they were pale and thin, and she was forced to disclose the whole story. When the father came to know about it, he was very angry. One day he went to the huk land along with Saima and She called for her sister’s lover i.e. the python. The python appeared before them and the father ultimately killed it. The head of the python was buried in the dungur, or waterfall. Raima forced her younger sister Saima, the eyewitness, to tell her what had happened. After knowing that her father had killed her beloved i.e. python, Raima became melancholic. The sisters while trying to locate where the head of the python was buried came across beautiful blooming khumpui (Hedychium coronarium) flowers. Hardly had Saima placed her tender hands on them, all the flowers withered instantly. Saima was shocked and called for her sister Raima. The same withered flowers touched by Saima became fresh as soon as the hands of Raima were placed on them. Raima began to call for her dongoi or beloved and her call was responded by the python and slowly the water in the dungur started to rise up. The water submerged the two lovers and united them, leaving Saima alone. Saima asked for advice from her sister as to how she will live all alone by herself. Raima, before she went underwater suggested that she should go to the nearby jungle, climb up a peepal tree there and start singing that she aspireed to become a queen and give birth to seven male children. 

One day, the Maharaja’s men came hunting in the jungle and heard Saima singing that her sole desire in life was to become a queen and give birth to seven male children. Feeling strange, the Maharaja’s men reported the matter to him. Immediately, the Maharaja’s men came and brought her down the peepal tree and took her to the palace. When Saima was brought before the Maharaja, she narrated the whole incident and the advice of her elder sister Raima. The Maharaja readily agreed to marry her and give her the status of a queen. All the other queens of the Maharaja became jealous of Saima. As days went by, Saima conceived and was prepared to give birth. All the other queens, jealous as they were, told the nurse that once she gives birth to the newborn child, he or she should be thrown in a pond. Further the nurse was instructed by the jealous queens to collect a few bamboo sticks to show that Saima gave birth to those sticks. 

Each time a child was born to Saima, the nurses would throw the new born baby in the pond, and place beside her a few bamboo sticks. It happened seven times, as Saima gave birth to seven children over the years. News began to spread far and wide that the Maharaja’s queen Saima gave birth to bamboo sticks rather than human beings. The Maharaja felt ashamed and humiliated and ordered that Saima be thrown out of the palace and be tied to a tree in the nearby jungle. In the meantime, the newborn children of Saima who were thrown in the pond began to grow. Each time the women of the palace would go to fetch water from the pond, the pitcher would be pierced and damaged altogether. The news of the incident again spread far and wide and the matter was reported to the Maharaja. The Maharaja asked his men to drain out the water of the pond and find out as to why pitchers were pierced as and when anyone goes to fetch water from the water tank.

As water began to be drained, to the surprise of everyone, seven handsome children were found playing. The seven children were asked about their identity but they were not able to tell. The Maharaja paraded one by one all the queens before the seven children and other women of the palace; the children did not identify any one of them as their mother. Rather they told the Maharaja that if any woman squeezed her breast and the flowing milk automatically came to their mouth, she would be their mother. Again all the queens, women of the palace and other women also tried but none of their milk reached the seven boys. Suddenly the Maharaja remembered Saima, the queen who was thrown out of the palace and left in the nearby jungle. The Maharaja sent his men to the jungle to bring her to the palace, and as per the instruction, Saima was asked to squeeze her breast, and the milk that flowed fell on the seven boys. This confirmed that they were the children of Saima. The Maharaja conducted an inquiry and found that the queens who were jealous of Saima instructed the nurse to throw the newborn babies in the pond, and keep beside her some pieces of bamboo. The queens responsible for the incident were punished, and thereafter the Maharaja, Saima and the seven children lived happily. 
Another important folk tale relating to water revolves around a brother and his younger sister. Here is the story: 

One day both the brother and sister were on their way to huk land. They had to cross a river, and on that particular day the river was in spate. The sister was ahead of her brother, and while trying to cross the river, she lifted her rignai (lower garments worn by Borok women) and the brother saw her thigh. He immediately fell in love with his own sister. When they got back from the jhum (huk or shifting cultivation) field, the boy appeared quite moody. The behavioural change in the boy was noticed by everyone in the family and ultimately the grandmother intervened and asked him about the changes in his mood. The boy told the grandmother that he wished to get married. The grandmother spelt out all the names of the young girls of the village whom the boy could get married to. The boy rejected all the young girls and ultimately the only young girl left was his own sister. The boy confessed that he had fallen in love with his own sister. 

In spite of counselling that it is wrong and unsocial on the part of a brother to fall in love with his own sister, the brother was unyielding and insisted on getting married. Thereafter, without much hype preparation began for the marriage. While the paddy was being dried under the sun in the courtyard for husking it into rice for the marriage, fowls began to feed on that paddy. The grandmother chased the fowls saying that the paddy being dried out was for the marriage of her grandson and granddaughter. The sister overheard what the grandmother said while chasing the fowls, and sought clarification about the marriage her grandmother was talking about; she was shocked to hear that her marriage was being fixed with her own brother. She was terribly upset about the whole thing and could not concentrate on her work. 

One day, she was told in her dream that if she wanted to get rid of her agony, she should plant a seedling of chethuang (Alstonia scholaris). She planted a chethuang seedling as instructed in her dream and poured water and worshiped. The tree began to grow, as she sang a song – ‘lokchethuanglok, anole dada bai se kainanihnwa (grow chethuang, grow, as preparation of my marriage with my own brother is going on) – and, after a while, as the tree grew sky-high, she mysteriously vanished in the air. But before she disappeared, her feet broke the shoot of the tree.

It’s because of this, the Borok people believe, the ‘chethuang’ is without a bud. Alstonia scholaris

References:
-    Debbarma, Debapriya, Treatise on Traditional Social Institutions of the Tripuri Community, Directorate of Research, Government of Tripura, Agartala, 1983. 
-    Lewin, T. H, The Hill Tracts of Chittagong and the Dwellers Therein (Reprint), Tribal Research Institute, Government of Mizoram, Aizawl, 2004.
-    L. B. Thanga, The Mizos: A study in Racial Personality, United Publishers, Guwahati, 1978. 
-    Rev. Dr. C. L. Hminga, The Life and Witness of the Churches in Mizoram, Baptist Church of Mizoram,Serkawn,1987. 
-    Devy G.N. &DebbarmaSukhendu, The languages of Tripura PLSI, Vol.28, Part-II, (Edited), Orient Brlackswan, Hyderabad, 2016, ISBN 978-81-250-6396-4