What makes a good Heavy Infantry Captain in CK3?

Employer has Positions Of Power Perk (Friend) +5, Martial Skill Martial × 2.5 (max 60), Prowess Skill Prowess (max 60), Strategist +20 and Has any Commander Trait +10 (the game's aptitude breakdown, patch 1.20.0.3).

What does the Heavy Infantry Captain give?

Terrible: Heavy Infantry Damage +5%, Heavy Infantry Screen +5%; Poor: Heavy Infantry Damage +10%, Heavy Infantry Screen +10%; Average: Heavy Infantry Damage +30%, Heavy Infantry Screen +30%; Good: Heavy Infantry Damage +40%, Heavy Infantry Screen +40%; Excellent: Heavy Infantry Damage +50%, Heavy Infantry Screen +50%.

Camp officers (landless adventurers)

Heavy Infantry Captain

Roads to Power

Heavy Infantry Captain is a camp officer in Crusader Kings III; its aptitude rests on Martial. At excellent aptitude it gives Heavy Infantry Damage +50%, Heavy Infantry Screen +50%. Aptitude also comes from Employer has Positions Of Power Perk (Friend) (+5), Strategist (+20) and Has any Commander Trait (+10). It needs Roads to Power. Patch 1.20.0.3, from game/common/court_positions/types/00_camp_officers.txt.

Quick answers (2)

What makes a good Heavy Infantry Captain in CK3?: Employer has Positions Of Power Perk (Friend) +5, Martial Skill Martial × 2.5 (max 60), Prowess Skill Prowess (max 60), Strategist +20 and Has any Commander Trait +10 (the game's aptitude breakdown, patch 1.20.0.3).
What does the Heavy Infantry Captain give?: Terrible: Heavy Infantry Damage +5%, Heavy Infantry Screen +5%; Poor: Heavy Infantry Damage +10%, Heavy Infantry Screen +10%; Average: Heavy Infantry Damage +30%, Heavy Infantry Screen +30%; Good: Heavy Infantry Damage +40%, Heavy Infantry Screen +40%; Excellent: Heavy Infantry Damage +50%, Heavy Infantry Screen +50%.

The Heavy Infantry Captain commands the camp's armored battle-line. They are responsible for the contingent's leadership, training, and tactics.

What it gives you, by aptitude

The holder's aptitude (see below) sets the level: levels start at 20, 40, 60, 80.

Terriblebelow 20
- Heavy Infantry Damage+5%
- Heavy Infantry Screen+5%
Poor20+
- Heavy Infantry Damage+10%
- Heavy Infantry Screen+10%
Average40+
- Heavy Infantry Damage+30%
- Heavy Infantry Screen+30%
Good60+
- Heavy Infantry Damage+40%
- Heavy Infantry Screen+40%
Excellent80+
- Heavy Infantry Damage+50%
- Heavy Infantry Screen+50%

What makes a good Heavy Infantry Captain

The game's own aptitude breakdown for this position — every part it adds up:

Part	Aptitude
Employer has Positions Of Power Perk (Friend)	+5
Martial Skill	Martial × 2.5 (max 60)
Prowess Skill	Prowess (max 60)
Strategist	+20
Has any Commander Trait	+10

The holder gets

Prestige+0.1/month

Who may hire it (valid_position) (10 lines of game script)

custom_tooltip = {
	text = landless_government_tt
	government_has_flag = government_is_landless_adventurer
}
custom_tooltip = {
	text = heavy_infantry_captain_captain_camp_officer_parameter_tt
	domicile ?= {
		has_domicile_parameter = camp_unlocks_heavy_infantry_captain_officer
	}
}

As written in game/common/court_positions/types/00_camp_officers.txt.

Who may hold it (valid_character) (3 lines of game script)

valid_camp_officer_trigger = {
	OFFICER = heavy_infantry_captain
}

As written in game/common/court_positions/types/00_camp_officers.txt.

Shown when (is_shown) (5 lines of game script)

has_ep3_dlc_trigger = yes
custom_tooltip = {
	text = landless_government_tt
	government_has_flag = government_is_landless_adventurer
}

As written in game/common/court_positions/types/00_camp_officers.txt.

Source: game/common/court_positions/types/00_camp_officers.txt, common/court_positions/tasks, common/script_values and the English localisation, Crusader Kings III 1.20.0.3. Salary is the base before the realm-size and cultural-era multipliers.