The Strategist (Tian Ji, 天机) star
The thinker: quick, adaptable, good with plans, and meets change as it comes.
One of the fourteen main stars of Purple Star Astrology (Zi Wei Dou Shu, 紫微斗数). They are not stars in the sky: they are fourteen named markers that your birth date and hour place around a ring of twelve palaces, and each palace stands for one part of life. What this star means depends on which palace it lands in.
When this site works out a chart’s type, it counts this star with the Ji Yue Tong Liang family (机月同梁): The Steward, built for structure — steady, capable, works best inside a system.
What the classic Zi Wei Dou Shu Quan Shu (紫微斗数全书) says it is
Wood, the third star of the southern dipper, the good star that lengthens the reckoning. Its transformed nature is called goodness (善), and getting its ground it acts and resolves the other stars' forward and backward motion. Fixing the reckoning in a person's chart, meeting the benefics gathered, then everything is good: diligent at worship, respectful to kin, at home among woods and springs, suited to a religious life. It has no cruel or unkind heart, and a quick and adaptable will. It sees the fish in the deep, and does things with method. A woman meeting it has blessing — favourable with the favourable, ill with the ill. Or holding the Body and meeting the Elder (天梁) as well, a high craft goes with the person. Master Xiyi (希夷先生) says: The Strategist (天机) is the star that lengthens life. Holding the Self it makes a person out of the ordinary; meeting the Elder, the two Aides (左右) and the Scholar and the Artist (昌曲), in civil life clear and prominent, in military loyal and good. Badly placed with the four malefics breaking in, it is a low chart and should be the quiet life of a monk. Where either limit meets it, a household is raised and made anew. A woman with benefics shining in is good for husband and children; with the Power transformation (化权) or the Fortune transformation (化禄), an honoured wife. The song runs: The Strategist is the ruler of Siblings, a true star of the southern dipper; it acts with plan and strategy, its nature the clearest of all, what it does it does best, and it may be counted among the company of the able. Meeting benefics it enjoys blessing; entering the pattern it sits in the academy. With the Voice (巨门) in one place, a military post commanding the frontier — and that too wants Power meeting the malefic before a name can be made. With the Elder in one place, certainly a monk or a recluse. With the Blessing (天同) and the Scholar and the Artist gathered and shining, prosperity. At Dragon (辰), Dog (戌), Rat (子) or Horse (午) well placed, a name and an office; at Tiger (寅) or Rabbit (卯) with the four malefics, the Disruptor (破军), the Blade (擎羊), the Millstone (陀罗), the Flare (火星) or the Ember (铃星) — meeting the malefics, calamity and empty alarms. With the Iron (武曲), the Voice, the Mystic (廉贞) and the Disruptor meeting, the two eyes have little light. When the two limits come to this star, things must change. Master Yuchan (玉蟾先生) says: The Strategist is the good star of the southern dipper, hence its transformed nature is called goodness. It assists the emperor's command in acting and resolves the ill stars' contrary turns. Fixing the reckoning within a person's chart: meeting benefics gathered it is wealth and rank; meeting a clashing malefic it is still fond of good. Filial and dutiful to kin, diligent at worship, with nothing unkind or unjust in it, and a will that reaches through and adapts. A woman meeting it mostly has blessing and long life. Well placed it has force; badly placed it has none.
答曰：天機屬木，南斗第三益算之善星也。後化氣曰善，又得地合之行事，解諸星之順逆。定數於人命，逢諸吉咸集，則萬事皆善。勤於禮佛，敬乎六親，利於林泉，宜於僧道。無惡虐不仁之心，有靈機應變之志。淵魚察見，作事有方。女命遇之為福，逢吉為吉，遇凶為凶。或守於身，更逢天梁，必有高藝隨身。習者宜詳玩之。希夷先生曰：天機益壽之星，若守身命，主人異常。與天梁、左右、昌曲交會，文為清顯，武為忠良。若居陷地，四殺沖破，是為下局，當為僧道之清閑。凡入二限逢之，興家創業更改。女人吉星拱照，主旺夫益子。有權祿則為貴婦。落局羊陀火忌沖破，歌曰天機兄弟主，南斗正曜星，作事有操略，稟性最高明，所為最好尚，亦可作群英會吉主享福，入格居翰林，巨門同一位，武職壓邊庭，亦要權逢殺，方可立功名天梁星同位，定作道與僧，女人若逢此，天同與昌曲，聚拱主華榮辰戌子午地，入廟有功名，若在寅卯位，四殺並破軍，羊陀及火鈴，若與諸殺會，災患有虛驚，武暗廉破會，兩目少光明，二限臨此宿，事必有變更。玉蟾先生曰：天機南斗善星，故化氣曰善。佐帝令以行事，解諸凶之逆節。定數於人命之中，若逢吉聚則為富貴，若逢沖殺亦必好善。孝義六親，勤於禮佛，無不仁不義之為，有靈通變達之志。女命逢之，多主福壽。其在廟旺有力，陷地無力。
One further clause here fixes a woman’s outcome by her sex. It is left out, in the Chinese as well as the English, as everywhere on this site.
The Strategist in each of the twelve palaces
Volume two of the classic goes palace by palace and says what each star does there. Each line below is its sentence for this star, translated. “Well placed” and “badly placed” refer to the star’s brightness in that branch.
Self palace (Ming Gong, 命宫)
who you are at core
With the Moon (太阴), the Elder (天梁) and the Sun (太阳) in accord: land and comfort for an ordinary person, and for an official the Merit transformation (化科), the Power transformation (化权) or the Fortune transformation (化禄) lifts the post. The Trouble transformation (化忌) in an idle palace, and neither money nor office brings honour — the family property spent, the life short, a wandering one. In a woman's chart with benefics, capable, and carrying more than her husband does.
天机属木，南斗化善星，为兄弟主。天机入男命吉凶诀：机月天梁合太阳，常人富足置田庄，官员得遇科权禄，职位高迁面帝王。天机化忌落闲宫，纵有财官亦不荣，退尽家财兼寿夭，飘蓬僧道住山中。天机入女命吉凶诀：天机女命吉星扶，作事操持过丈夫，权禄宫中逢守照，荣膺诰命贵无伦。天机星与太阴同，衣禄丰饶终不美，天机入限吉凶诀：男女二限值天机，科权禄逢大有为，出入经营多遇贵，发财发福少人知。天机照限不安宁，家事纷纷外事多，更遇羊陀并巨暗，须知此岁入南柯。
Part of this clause fixes a woman’s outcome by her sex; it is left out here, as everywhere on this site.
Siblings palace (Xiong Di, 兄弟)
siblings, and the people alongside you
Well placed, two. With the Voice (巨门), two. Badly placed, at odds and not of one mind. With the Elder (天梁), two; with the Moon (太阴), two or three. With the Blade, Millstone, Flare and Ember (羊陀火铃), siblings exist but with harm.
天机庙旺有二人，与巨门同二人，陷地，相背不一心，天梁同二人，太阴同二三人，见羊陀火铃虽有而克害。
Spouse palace (Fu Qi, 夫妻)
marriage and close partnership
Suits a young and strong partner; a wife may take an older husband. With the Blade, Millstone, Flare and Ember (羊陀火铃), parting while both live. Marrying late is fortunate. With the Elder (天梁), an older partner suits; with the Moon (太阴), a helpmeet, and good-looking.
天机宜年少刚强之，妻可配夫宜长，加羊陀火铃主生离，晚娶吉，天梁同宜年长，太阴同内助美容。
Children palace (Zi Nü, the Children palace (子女))
children, and what you create
Well placed, two, or several by a concubine. With the Voice (巨门), one. With the Elder (天梁) at Tiger (寅), two or three; at Monkey (申), more daughters than sons and only one son. With the Moon (太阴), two or three. With the six malefics, no children at all.
天机庙旺二人，或庶生多，巨门一人，天梁同在寅宫，有二三人，在申宫女多男少，只可一子，太阴同二三人，加羊陀火铃空劫全无子。
Wealth palace (Cai Bo, 财帛)
money coming in and going out
Money made by effort and worry. With the Voice (巨门), taken from busy places; with the Elder (天梁), made by ingenuity and from outside the usual course; with the Moon (太阴) badly placed, gains and losses. With the six malefics, a lifetime of both.
天机劳心费力生财，巨门同闹中求取，天梁同机关巧计生外财，太阴同陷宫成败，加羊陀火铃空劫一生有成有败。
Health palace (Ji E, the Health palace (疾厄))
the body, and what wears it down
Much illness in infancy; badly placed, injury to the head or face. With the Voice (巨门), blood disorders; with the Elder (天梁), complaints of the lower body; with the Moon (太阴), skin sores. With the Blade (羊) and Fire (火) badly placed, eye trouble and weakness in the limbs.
天机襁褓多灾，陷地头面破相，巨门同血气疾，天梁同下部疾，太阴同疮灾，加羊火陷宫有目疾，四肢无力。
Travel palace (Qian Yi, 迁移)
going out — travel, moving, elsewhere
Patrons met abroad; disputes at home. With the Voice (巨门), fortune lies in movement; with the Elder (天梁), going out answers; with the Moon (太阴), fortune in busyness. With the Blade, Millstone, Flare and Ember (羊陀火铃), disputes abroad and no rest.
天机出外遇贵居家有是非，巨门同动中则吉，天梁同出外称意，太阴同忙中吉，加羊陀火铃在外多是非身不安静。
Friends palace (Pu Yi, 仆役)
friends and the people you work with
Well placed, capable; badly placed or empty, they resent you. With the Elder (天梁), they come late; with the Moon (太阴), they fall short. With the Voice (巨门) and benefics, servants; with none of it works (擎陀火铃空劫).
天机入庙得力，陷空怨主，天梁同晚招，太阴同欠力，巨门加吉星有奴婢，加擎陀火铃空劫全难。
Career palace (Guan Lu, 官禄)
work and standing
Well placed, authority and standing; meeting the Artist (文曲), a good minister. With the Blade, Millstone, Flare and Ember (羊陀火铃), only then is it suitable. With the Elder (天梁), fit for civil or military; with the Moon (太阴), a name known at the frontier. Badly placed, office lost and rank forfeited — a clerk's footing.
天机入庙权贵，会文曲为良巨，见羊陀火铃方宜，天梁同文武之材，太阴同名振边夷，陷宫退官失职，吏员立脚。
Property palace (Tian Zhai, 田宅)
home, property, what you keep
The inheritance recedes and new property is built. With the Voice (巨门) at Rabbit (卯), farmland; at Rooster (酉), the inheritance is not kept — large first and small after. With the Elder (天梁), property acquired and wealth in later years; with the Moon (太阴), acquired by your own hand and prosperous.
天机退祖新创置，巨门同在卯宫有田庄，在酉宫不守祖业，先大后小，天梁同有置晚年富，太阴同自置旺相。
Wellbeing palace (Fu De, 福德)
peace of mind, and what you enjoy
Toil first and ease after. With the Voice (巨门), effort and little peace; with the Elder (天梁), contentment; with the Moon (太阴), gladness. With the six malefics, hurrying about and never still.
天机先劳后逸，巨门同劳力欠安，天梁同享福，太阴同主快乐，加羊陀火铃空劫奔走不得宁静。
Parents palace (Fu Mu, 父母)
parents, and anyone with authority over you
Well placed, no harm. Badly placed and meeting the six malefics, raised under two surnames, a second set of parents, adopted out or married in. With the Moon (太阴), harm avoided; with the Elder (天梁), none — both require no malefics present, and with them harm is not avoided. With the Voice (巨门), harm early.
天机庙旺无刑，陷地逢羊陀火铃空劫，二姓寄居，重拜父母，或过房入赘，太阴同免刑，天梁同无刑，俱要无杀，加有杀，加也不免刑伤，巨门早刑。
Which star is in your Self palace?
That needs your birth hour and place. The chart corrects the hour to true solar time, using the timezone actually in force in your birth year.
The other thirteen: The Emperor · The Sun · The Iron · The Blessing · The Mystic · The Treasury · The Moon · The Wolf · The Voice · The Minister · The Elder · The General · The Disruptor.