Penetrator is an augment for a Throwing Knife, not a separate Legendary weapon. To find one, look for a Throwing Knife whose item card lists the Penetrator Augment. Its critical-hit behavior has been adjusted, so older claims that it guarantees critical hits should not be treated as current mechanics.
Is the Penetrator Throwing Knife legendary?
No. Game8 describes a Throwing Knife with Penetrator as not being a Legendary weapon: Penetrator is the augment on the knife, not a standalone item rarity or weapon. When checking loot, inspect the item card for the augment rather than searching for an item named “Legendary Penetrator.” Game8’s Throwing Knife guide and Android Experto’s guide discuss the item in those terms.
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What does the Penetrator Augment do now?
The official balance notes document two changes in October 2025. On October 23, Gearbox Entertainment reduced the critical chance on the Jakobs crit knife to 30%. On October 30, the developer notes said the Penetrator Augment had been corrected because it was unintentionally setting all attacks to a 30% critical chance. The October 30 note establishes that the earlier behavior was unintended; it does not establish the augment’s exact behavior in every later game version.
For that reason, treat older descriptions of Penetrator as a guaranteed critical-hit effect—or claims specifying an exact effect window—as unverified unless they match the current in-game item and a newer authoritative update. The official notes are available from Borderlands 4 news and patch notes.
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How to farm a Throwing Knife with Penetrator
There is no official drop table or confirmed guaranteed source for the Penetrator Augment in the cited material. Guides report repeatable options, but neither route is established as the best or as a guaranteed drop.
| Reported route | What to expect | Drop guarantee |
|---|---|---|
| Encore Machine boss encounters | Game8 recommends replaying boss encounters through Encore Machines to look for Throwing Knives. Repeated runs create more opportunities to check loot. | None established by the cited guide or official notes. |
| Driller Hole | Android Experto reports Driller Hole as a repeatable farm and describes Penetrator as a world drop. | None established by the cited guide or official notes. |
Choose a repeatable activity you can clear comfortably, then inspect eligible Throwing Knife drops for Penetrator. The sources do not provide measured drop rates, so they cannot support a reliable ranking of these routes by efficiency.
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How to use Penetrator in a build
Think of a Penetrator knife as a possible build-enabling utility item, not a guaranteed damage multiplier. PC Gamer has discussed pairing a Penetrator Throwing Knife with the Quincunx Stellium, but that is secondary build coverage from before the official correction. The pairing is a lead to consider, not proof of a universal result under the corrected or current mechanics. PC Gamer’s Borderlands coverage provides that build context.
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