Amidst all the characters of Mahabharat , Ashwatthama's character always attracted me perhaps because he is one among the seven Chiranjivi. Would like to tell you the story of his origins
During Samudra Manthan , Halahaal the fuming posion capable of burning universe appeared and all Dev Danav Manav Yaksha Gandharva fled. All of them along with Lord Vishnu and Lord Bramha came to Lord Shiva. Lord Shiva consumed Halahaal and held it in his throat. However unable to bear its consequences it started burning him. The Vish purush sprung out of him folded his palms , Lord Shiva asked him that although Lord Vishnu and me didn't let you kill the people yet in Dwapar Yuga during Mahabharat war with my blessings you will be able to kill oppressive kshatriyas later you will assume the post of Saptarishis in following Manvantar. You will be born as Bhardwaja's grandson and be raised as Brahman but attracted towards Kshatriyahood.
In Mahābhārata, Ashwatthama was son of Guru Dronacharya and Kripi.
His parents were ayonij that is they were not gestated in the human womb. Drona got his name as he was gestated in a "drona" [vessel made of leaves]. From his fathers' side Ashwatthama traces his roots to Maharshi Angiras [who was saptarishi in first Manvantar during rule of swayambhu Manu] , his paternal grandfather is Maharashi Bhardwaj [ Saptarishi of present Manvantar governed by Vaivaiswat Manu] , his maternal grandfather is Rishi Shardwan a divine saint who was more interested in archery than Vedas. He meditated and attained the art of all sorts of Divyastra . He was such a great archer that no one could defeat him]. Ahwatthama's great great maternal grandfather is Maharshi Gautam [ also a Saptarishi of present Manvantar]. Needless to say being born in family of Saptarishis
and to pious parents like Dronacharya and Kripi , he inherited their wisdom and teja. Being born to Drona he is also called "Draauni". He had a gem stone embedded on his forehead. When he was born he made a loud cry like Indra's horses, he was named as Ashwatthaamaa by an akashvani. (Reference : MBH, 6-War/27) His childhood passed in a very poor condition as his father didn't get any job.
His maternal uncle was Kripacharya. He and his uncle Kripacharya along with Hanuman ji are the only three living people who actually witnessed events of Mahabharat and played pivotal role in the great war.
Once baby Ashwatthama was very hungry, Drone saw Kripee giving him flour mixed water instead of milk. He felt very sad and went to his old time friend Drupad to ask for one cow for his son. But he refused to give it. Drona vowed to take revenge from Drupad. He later met Kuarava and Pandav and took out their ball from well and was subsequently appointed as their Guru by Bhishm.
Ashwatthaamaa was very mighty and skilled in warfare. He fought very bravely in Mahaabhaarat war from Duryodhan's side. He was jealous of Arjun as he was exceptionally well in archery , virtue and favourite of his father but his anger bursts out only after Pandavas kill drona by deciet.He took his father's assassination very much to his heart and in his disturbed mental status he vowed to exterminate Pandavs just like what Lord Parshuram did to exterminate oppressive Kshatriyas.
Untill Dronacharya dies his role was insignificant but he rises to prominence only after death of Karna when he promises Duryodhan that he will kill the Pandavs.
Source : Vishnu Puraan
The story is explained in detail in Sauptika Parva [The book of sleeping warriors] of Mahabharat.
SHalya was killed by Yudhishthira and the entire Kauravan army gets killed. Duryodhana initially fleds in jungle and hides in pond and fights Vrikodara [ Bhimasena ]. As he was blessed by his mother Duryodhana's body becomes as hard as Vajra and hence Lord Krishna hints [Vrikodara] to smash his thigh. Vrikodar does so and Duryodhana lies there waiting for his death abusing Pandavas.
The three Kauravan survivers left were Kripacharya , Kritverma [ Yadav and commander in chief of Narayani Sena] and Ashwatthama. Highly upset by the fall of their King they were sitting under a great banyan tree. Frustated Ashwatthama remembers how his father was insulted by Drupada, and his daughter married Pandavas , her brother Drishtyadyumna beheaded his father when he was in state of meditation and Yudhishthira's lie that
"Ashwatthama hatah iti narova kunjarova"
Ashwatthama was killed don't know if its man or elephant.
He also remembered that the whole plan was hatched by Lord Krishna himself who together with Pandavas boasted that theirs is side of Dharma. Very disturbed restless and incesed Ashwatthama observed how an owl, attacked and harrassed by crows in the morning, attacked back at night and killed them. He realized that war was best fought from a position of strength. He got up and together with Kripacharya and Kritverma went to Duryodhana and found him there lying half dead besides the pond . He asked Duryodhan - "I will bring five Paandav's heads for you . Just wait for me, don't go away." and he went away immediately. Kripa tried to dissuade him from doing this adharma but he didn't listened to him. Kritaverma and Kripa accompanies him to Pandavan camp. There they see a ferocious demon guarding Pandavan camp he was having thousand eyes. This demon was none other than Mahakal Rudra who was guarding Pandavan camp as requested by Lord Krishna. Ashwatthama tried to win the demon but failed finally he realized who the demon was and decided to worship Mahakal and offered himself as sacrifice . Mahakal Rudra got impressed by Ashwatthama and said "I was guarding Pandavas as I was instructed by Krishna to do so , now their Kaal has come" he handed his Chandrahaas sword to Ashwatthama and entered his body. Ashwatthama was now possessed by Mahakal Rudra.
Ashwatthama charged the Pandavan camp and wreaked havoc. He kicked Dhristadumnya, to death as his punishment for Guru hatya. Shikhandi the transgender Panchal prince and Bhisma's assasin was hacked in to pieces and thousands of other Pandava warriors were mercilessly put to the edge of Ashwatthama's sword and perished. Those who tried fleeing away were killed down by Kripacharyya and Kritavarma who were positioned at the camp's entrance. Ashwatthama sustained numerous wounds and injuries in this battle but nothing could stop him from executing his vow. Ashwatthama killed Draupadi's five sons believing them to be the Pandava brothers. There after they set fire to Pandavan Camp and celebrated they went to tell this news to Duryodhan but he was dead by then. Ashwatthama then went to Vyas Ashram. Where he was followed by Pandavas and he invoked Bramhastra in a grass blade and fired it for the destruction of Pandavas , Arjuna too launched his bramhastra to counter Ashwatthama's. Bramhajee appeared between the two Bramhastras and commanded both of them to call off their astras as it may burn the entire universe. Arjuna was able to call his Bramhastra but Ashwatthama couldn't do so , he re routed the Bramhastra to the womb of Uttara , Abhimanyu's wife. Bramhastra burned down the fetus. Angered by Ashwatthama's cowardice Pandavas decided to kill him but Krishna asked them to pull out the gem embedded on his forehead and cursed him to be leper and roam for 3000 years.
Ashwatthama is destined to be Saptarishi in next Manvantar [The eighth Manvantar] The Saptarishis of this manvantar will be--Ashwatthama, Rishyashringa, Kripacharya, Galav, Shatanand, Kaashyap and Parashuram. . This Manvantar will be governed by Surya's son Savarni Manu and hence the Manvantar will be called as Savarnya.
Source: Padma Puran,(SB 8.13.12,17, Garuda Purana 1.87.36).
There had been several news articles published in the newspaper reporting sighting of a very old man having dent on his forehead in various places of India , you may find them on internet. Closing the thread I will only say that amongst the Hindu people it is believed that inorder to get long life , luck fame and properity following mantra should be recited every day :-
"Ashwathaama Balir Vyaso Hanumanash cha Vibhishana Krupacharya cha Parashuramam Saptatah Chirjeevanam"
Ashwathama, King Bali, Ved Vyasa, Hanuman, Vibhishana (Ravana's Brother), Krupacharya and Parashurama are death-defying or imperishable personalities.
Nevetheless Ashwatthama comes first in the shloka while remembering the Chiranjivis as he is partial incarnation of Lord Shiva and that makes him the 12th rudra. These Chiranjivins are worshipped along with 11 adityas , 8 vasus and Ganeshji before observing any Paath , Anushthaan , Religious austerities.