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Not much is known about Chos grags bzang po, sometimes mistaken for Klong chen pa’s son. In addition to the biography that interests us, another of his works is preserved: History of the Essential Drop of the ḍākiṇī, a Garland of Jewels (mKha’ ’gro snying thig gi lo rgyus rin chen phreng ba - pp. 556-609 of the section of mKha’ ’gro snying thig in which it is included). However, this text contains some autobiographical pages (p. 602-607).
Here is what we can learn from it.
Originally from Eastern Tibet, Chos grags bzang po went, in his fifteenth year, to ’Bri gung, in central Tibet, and received the minor ordination there.
Until his twenty-first year, by his own admission, he wasted his time; then, as a result of a vision telling him that he would die if he did not practice the Dharma, he took full ordination in his twenty-fifth year. It was then that he met Klong chen rab ’byams. The corresponding passage in the mKha’ ’gro snying thig gi lo rgyus rin chen phreng ba (p. 604) is, to our knowledge, the only direct record of Klong chen rab ’byams’ teaching.
Chos grags bzang po was also the student of other masters, Blo bzang pa, rGyal rong pa, Tsā ri pa, Yon tan rgya mtsho, Chos rje kun mkhyen pa, Paṇ chen pa, lHa khang pa, Rin chen gling pa,  and finally sPrul sku Legs ldan pa, that is, rGyal sras Legs pa or Legs pa’i rgyal mtshan, the chief disciple of Padma las ’brel rtsal, who will be discussed again below (we have placed him at the end of the list of Klong chen rab ’byams masters).
From an examination of this short autobiographical text, one can draw the conclusion that Chos grags bzang po was certainly a good meditator (rGyal sras Legs pa finally gave him permission to teach), but probably not a scholarly master, given the late and mainly tantric character of his training. Like many practitioners of this time, he does not strictly belong to one stream or another; but there is clearly a dominant pattern of both rDzogs chen pa and jo nang pa, with some minor bka’ brgyud pa elements, in the teachings he received.
He is mentioned by sMyo shul mkhan po in his list of the principal disciples of Klong chen rab ’byams (sMyo shul chos ’byung, vol. I, p. 345) under the name ’Dan sgom Chos grags bzang po. This author devotes a short biography to him (ibid, vol. II, pp. 91-96).
Chos grags bzang po is also the recipient of a small writing by our author, entitled Sems dang ye shes kyi dris lan (n° 271).
One should take into consideration the fact that Chos grags bzang po may have had an essentially jo nang pa background. The question of Klong chen rab ’byams’ relationship (or lack thereof) to this tradition is interesting for several reasons, as we shall see; but, at the same time, it is very poorly documented. The Sems dang ye shes kyi dris lan should therefore be reread in this perspective. In any case, Chos grags bzang po is reputed to have expressed his admiration for Klong chen rab ’byams in a series of verses in which he compares him to other illustrious masters of his time; two of them are of interest to us here:
No sooner have we glanced at the writings of the Great Omniscient
That the works of Bu[ston], Dol[po pa], and Shāk appear dull.
If these verses are indeed by this author, he appears, in short, as a Khams pa, trained in gSang phu as far as philosophy is concerned, having then deepened the Kālacakra notably with masters jo nang pa before turning to rDzogs chen, apparently abandoning the doctrine of Jo nang.
One might wonder whether, through the way he calls himself “supreme son of [this] father” in the mKha’ ’gro snying thig gi lo rgyus rin chen phreng ba, Chos grags bzang po might not be posing as Klong chen rab ’byams’ successor in his spiritual lineage. The title of slob dpon given to him by the master of Gangs ri thod dkar could be an indication of a distinguished rank among his disciples. Indeed, even though Chos grags bzang po disappears from the most common later presentations of the lineage, sMyo shul mkhan po tells us (op. cit. p. 94) that he had a significant spiritual posterity, particularly through his disciples Ngam ston Nyi ma ’od zer and Kaḥ thog pa rdo rje ’bum pa.
In any case, it was the recipient of the clarifications of the Sems dang ye shes kyi dris lan who wrote the Life Worth Seeing (mThong ba don ldan), which is fairly composed, but does not bear the mark of a deep personal knowledge of the Klong chen pa’s works.
Let us add that the gross bibliographical errors in the table of works (similar to The Inventory of the Treasure of Jewels (dKar chag rin po che'i mdzod khang) falsely attributed to Klong chen rab ’byams himself) on which this biography ends, if they are surprising on the part of a close disciple of the latter, could paradoxically be the indication of a rather high date of composition. Indeed, their presence is more understandable in an author who does not have first-hand information, thus at a time when no xylographic edition of Klong chen rab 'byams' works had yet been produced.
One wonders whether the Inventory of the Treasure of Jewels (dKar chag rin po che’i mdzod khang), far from being the source of the table of works found in the biography of which Chos grags bzang po is the author, might not have been extracted from it, before being falsely imputed to Klong chen rab 'byams. This is what we are led to believe: a composition old enough to explain, as we have just said, the ignorance of the work of Klong chen rab 'byams (certainly still in the state of manuscripts, dispersed or made inaccessible by circumstances unknown to us, notably the long exile of Klong chen rab ’byams in Bhutan), and to cause confusion with the works of this author (attribution to Klong chen rab 'byams of this inventory of his works, which cannot reasonably be in his hand).
 This is indeed a confusion, for it is clear from the hagiographies that Klong chen rab ’byams’son was called sPrul sku Grags pa ’od zer (Zla ba grags pa, sometimes confused with the latter, is his son, and therefore Klong chen rab ’byams’ grandson). The basis for this confusion of Chos grags bzang po and Grags pa ’od zer may come from the fact that the biographer calls himself, in the colophon, “supreme son of [this] father” (pha yi bu mchog). But it is clear that this is a purely spiritual filiation, especially since the author presents himself as coming from Eastern Tibet (Chos grags bzang po mdo khams pa) : Klong chen pa was from Central Tibet. Nevertheless, the formula “supreme son of [this] father” confirms that he is a direct disciple of Klong chen rab ’byams.
 According to what the letter of the autobiography suggests; a few years later according to our calculation. We return to Chos grags bzang po in the second section of this work, where this character interests us as a contact between Klong chen rab ’byams and the master jo nang pa Dol po pa Shes rab rgyal mtshan.
 He received the Ṣaḍaṅgayoga of Kālacakra from this master. This immediately brings to mind the master jo nang pa of that name, the master of Dol po pa Shes rab rgyal mtshan. Now this Yon tan rgya mtsho died in 1327. To have been his disciple, one must assume that Chos grags bzang po, who came to central Tibet (where Yon tan rgya mtsho was active) only in his fifteenth year, was in fact of the same generation as Klong chen rab 'byams (i.e., he was born no later than the early years of the fourteenth century). Of course, his biography of Klong chen rab ’byams includes an account of the latter’s death; but, since it occurred in Klong chen pa's fifty-sixth year, there is nothing to prevent a contemporary, even an older one, from having survived him to relate this episode. sMyo shul mkhan po (op. cit., II, p. 96) tells us that Chos grags bzang po died in his seventy-fifth year. He must therefore have lived approximately between 1300 and 1375.
 In context, since it is not Klong chen rab ’byams, this “omniscient lord of the Dharma” can only be Dol po pa Shes rab rgyal mtshan, especially since Chos grags bzang po also received teachings relating to Kālacakra, a specialty of the Jo nang pa, from him. The proximity of Yon tan rgya mtsho’s name makes this strong presumption a certainty.
 Paṇ chen Phyogs las rnam rgyal (1306-1386), a disciple of Dol po pa Shes rab rgyal mtshan, who was often referred to as such at that time. Again, this is confirmed by the fact that Chos grags bzang po studied the Vimalaprabhā (great commentary on the Kālacakra-tantra) with him.
 A disciple of Padma las ’brel rtsal, predecessor of Klong chen rab ’byams in the revelation of the mKha’ ’gro snying thig ; jis biography can be found in the Zab mo’i gter dang gter ston grub thob ji ltar byon pa'i lo rgyus mdor bsdus bkod pa Rin chen bai dū rya’i phreng ba of Kong sprul, and will be returned to later in the chapter on rGyal sras Legs pa and the transmission of mKha' 'gro snying thig.
 The biography of Karma pa Rang byung rdo rje in the Deb sngon mentions a certain Śākya gZhon nu, abbot of the lower monastery of gSang phu in 1302. Perhaps this is the personage in question.
 bsTan bcos kyi dKar chag rin po che'i mdzod khang. This bizarre and even fanciful text was, however, incorporated into the gSung ’bum of the Po ta la (cf. Gene Smith's TBRC database, which states that this text comprises “7 ff. in vol. 10 of the 11 vol. gsung ’bum in the Potala collection.” It is known to us through a modern reworking of the sDe dge ed. of the gSung thor bu.
 The first xylographic edition of a work by Klong chen rab ’byams is that of Theg mchog rin po che’i mdzod which can be dated to 1533 according to F.-K. Ehrhard (2000).
 We ourselves witnessed a pious falsification of this kind by a lama who was perhaps more zealous than enlightened: he even explained to us the reasons (quite political) why he had seen fit to change a name in a traditional text. It is impossible to know how common this practice is, but this master obviously did not feel that he was doing anything serious.
The next chapter of this biography is here.