The Disruptor (Po Jun, 破军) in the Self palace (Ming Gong, 命宫)

What the classic says, Zi Wei Dou Shu Quan Shu (紫微斗数全书), volume two

With the Flare (火星) or the Ember (铃星) sharing the palace, a hard heart. Well placed with the General (七杀) and the Wolf (贪狼), a hero not to be withstood — the text names Guan Yu (关羽) — and for an ordinary person, land and comfort. At Rat (子) or Horse (午) with the Scholar (文昌) and the two Aides (左右) both, ample means and open-handed, and office plainly held. The Fortune transformation (化禄), the Merit transformation (化科) or the Power transformation (化权) on it is unusually good. Badly placed with malefics added, the ancestral line broken and a life far from home. Not welcome in the body palace: with the Mystic (廉贞), the Flare, the Blade (擎羊) and the Millstone (陀罗) it turns ill — if not injury, then a short life. At Rat or Horse in a woman's chart it is well placed: blessing and long life, able, out of the common run, good for husband and children.

破军火铃同，狗悻狼心。破军七杀来相会，羊陀火铃最所忌，孤刑克害六亲无，只可偏房与侍婢。破军水，北斗化耗星，主妻子、奴仆。破军入男命吉凶诀：破军七杀与贪狼，入庙英雄不可当，关羽命逢为上将，庶人富足置田庄。破军子午会文昌，左右双双入庙廊，财帛丰盈多慷慨，禄官昭著佐君王。破军一曜最难当，化禄科权喜异常，若还陷地仍加杀，破祖离宗出远乡。破军不喜在身宫，廉贞火羊陀会凶，不见伤残定寿夭，只宜僧道度平生。破军入女命吉凶诀：破军子午为入庙，女命逢之福寿昌，性格有能偏出众，旺夫益子姓名香。破军女命不宜逢，擎羊加陷便为凶，须教悲哭度朝昏。破军入限吉凶诀：破军入限要推详，庙地方知福禄昌，更遇文昌同魁钺，限临此地极风光。破军入限细推详，庙地无凶少损伤，杀凑破军防破耗，更防妻子自身亡。破军主限多浓血，失脱乖张不可说，更值女人主孝服，血光产难灾殃节。

Part of this clause fixes a woman’s outcome by her sex; it is left out here, in the Chinese as well as the English, as everywhere on this site.

“Well placed” and “badly placed” refer to the star’s brightness in the branch the palace falls on: the same star in the same palace reads differently bright and dim, and the clause says how.

Source

And in the chapter of questions on the stars (Zhu Xing Wen Da Lun, 諸星問答論)

poorly placed, leaves the ancestral line behind

在身命陷地，棄祖離宗

How this placement actually turns up

• Well placed (exalted or strong) in 52% of those charts, badly placed (fallen) in 16%, in between the rest.
• Alone in the palace in 50%; sharing it with The Iron (武曲) 17%, The Emperor (紫微) 17%, The Mystic (廉贞) 16%.
• Carries a birth-year transformation in 22%: Fortune (化禄) 10%, Power (化权) 12%.
• How often the conditions the classic’s line names actually occur — one of the four difficult stars (擎羊陀罗火星铃星) in the palace with it: 30%; one of the six helper stars (左辅右弼文昌文曲天魁天钺) with it: 41%; Lu Cun (禄存) with it: 8%.

Counted by casting every day from 1950 to 2009 at each of the twelve hours — 262,980 charts, 8.3% of which have The Disruptor here (every main star sits in every palace in about one chart in twelve). A count, not a reading.