The Head Kohen is above the Kohen Leading the Army and the Replacement Head Kohen: Yoma 73a
The Head Kohen is responsible to pray for the welfare of the nation: Makkot 11a
The Head Kohen's Family
Whether a substitute wife was set up for the Head Kohen to marry on Yom Kippur, if his wife would die, so that he could serve as a married man: Succah 24a
Under the rule forbidding the Head Kohen's marriage to a woman who isn't a virgin, "virgin" refers to a woman who has never had sexual intercourse: Niddah 8b
The mother of the Head Kohen would provide food and garb for accidental murderers, to keep them from praying for the Head Kohen to die: Makkot 11a
What would happen if a Head Kohen attempted to marry a widow: Temurah 5b
Certain Specific Head Kohanim
Head Kohanim who ruled by force: Pesachim 57a
The Temple's Outer Room cried out against the presence of Yissaschar Ish Kefar Barkai: Pesachim 57a
Yissaschar Ish Kefar Barkai used to disdain the actual Temple Service, covering his hand with a silk covering: Pesachim 57a
Punishment of Yissaschar Ish Kefar Barkai: Pesachim 57a-b
Yishmael Ben Peachi was a good Head Kohen, and the Temple's Outer Room cried out for his presence: Pesachim 57a
Yochanan Ben Narbai was a good Head Kohen, and the Temple's Outer Room cried out for his presence: Pesachim 57a
R' Yishmael Ben Kimchit: Yoma 47a
R' Yosef ben Ulam, of Tzippori: Megillah 9b
Merit of Kimchit, causing her to have 7 sons who were Head Kohanim: Yoma 47a