The Shinobi Infiltrator armor is a melee-oriented armor set purchased from the Tavernkeep for 225 , after Golem has been defeated. The set consists of the Shinobi Infiltrator's Helmet, Shinobi Infiltrator's Torso, and Shinobi Infiltrator's Pants.
The torso can be swapped out for the Valhalla Knight's Breastplate to greatly increase one's defensive capabilities without sacrificing melee damage, which can be useful if you decide to prioritize general melee combat over the use of sentries.
The total bonus to max number of sentries is +3, allowing 4 to be summoned at once.
A ninja (忍者) or shinobi (忍び) was a covert agent or mercenary in feudal Japan. The functions of the ninja included espionage, sabotage, infiltration, and assassination, and open combat in certain situations.