Artyom first hears about Lesnitsky from Alex, a guard in D6, who asks Uhlman if he had heard about what Lesnitsky did. A second guard on the D6 elevator system says that Lesnitsky had ransacked the lab. Lesnitsky is first seen when Artyom is captured in the Red Line, alongside General Korbut. Lesnitsky informs Korbut of Artyom's achievements as a Ranger and that Miller trusts him.
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Lesnitsky leads a Red assault on the Ranger Church base on the surface and takes Anna, Miller's daughter and Artyom's partner, to Oktyabraskaya as a hostage. Lesnitsky leads the Reds in massacring the inhabitants of Oktyabraskaya and burning the station down. Artyom confronts Lesnitsky at the end of the station where he holds Anna at knifepoint, ordering Artyom to remove his gas mask or else he will slit Anna's throat. Artyom can either comply or retaliate by shooting Lesnitsky's mask off; either choice will lead to Lesnitsky throwing Anna at Artyom.
Lesnitsky is later confronted by Artyom on the surface, where Artyom eventually subdues him with the help of the Baby Dark One. From this point the player may choose the fate of Lesnitsky: give him retribution for his actions and kill him, or forgive him and knock him unconscious. While there is no instant benefit of either sparing or killing Lesnitsky, killing him grants negative Moral Points and almost certainly guarantees the destruction of D6 during the C'est la Vieending, while sparing him contributes towards the Redemption ending where Artyom alternatively saves D6.
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Lesnitsky's surname (Лесницкий) is a native Slavonic one derived from the Slavic word for forest (лес or las depending on the language); it is very similar to the Polish surname Leśnicki, pronounced more or less the same.
Lesnitsky's headwear constantly changes. In the Red Line he is seen wearing a pilotka hat, in the Church and Oktybrskaya he is seen with the Ranger signature helmet, and in his final encounter on the surface he wears a hat similar to Pavel Morozov's.
He has met and worked with Anna extensively, as Anna recognizes his voice.
He isn't completely up to date on Intel concerning Sparta, as he possesses an out of date passcode for the church he believed was still in use. This was likely because of his withdrawal from his position as a Ranger spy by the Red Line after securing a biological weapon and in preparation for the upcoming war. This does suggest the Red Line did not possess anymore spies within the Spartan Order, at least none with access to much intelligence concerning the church base.
He seems to have no idea that there is a catacomb system below the church base also, however, his team survived through the dangerous catacomb and made it to Oktyabraskaya before Artyom did.
It is speculated that he must have been a deep cover spy working within the Rangers prior to Artyom contacting Miller about the Dark Ones. The time period between finding D6 and Lesnitsky stealing the virus is too short for him to be trusted such an important and dangerous item.
One Ranger outside Artyom's quarters mentions that it took him two years to train to be a ranger. As Metro: Last Light takes place roughly a year after Metro 2033, it would be highly unlikely that Lesnitsky would have been trusted with such duties.