The Yagyu Darkblade (柳生の漆黒, Yagyu no Shikkoku?, lit. Yagyu's Jet Black) is the strongest Ninja Sword available in Final Fantasy XII. Its license can be found in the top-left section of the weapon area of the License Board, along with other Ninja Swords costing 80 LP. The weapon has an Attack power of 80 and a Combo rate of 22%. Similar to other Ninja Swords, Yagyu Darkblade is Dark-elemental, and grants the user +20 to Evasion. Ninja Swords are among the fastest weapons in Final Fantasy XII with 1.97s charge and 1.2s action time; only daggers are faster.
Players can only fight Bombshells in Lhusu Mines-Lasche Span. To stack up the odds upon players, the Bombshell has a spawning rate of 20% only, therefore players should zone between Lasche Span's entry and exit or either Site 5 and Site 11 a few times. There are also two Aeronites, both yielding up to Level 60 in the area, and can be very tough to defeat.
A popular tactic of chaining Bombshell is to lure it to one of the end of Lasche Span to the other, since the Aeronites will stop pursuing the party after a fixed point of the bridge. Set gambits to "Foe: Water-weak-->Attack" as this will encourage the party members to attack Bombshell only. Once you do this, head towards either Site 5 or Site 11, whichever is closer. Alternately, Aeronites can be killed by poison (which does not break the chain). If using this method, you can speed it up greatly with additional gambits such as "Foe: HP>=2000: 1000 Needles" or "Foe:HP>=5000:Attack".
Players need to zone twice to reset the area and re-spawn Bombshell, therefore, the most efficient way is to ride the mine cart in either area, which will count as two zones. Players are, however, encouraged to turn off Gambits so the party will not attack the stray Vampyr bats.
Once reaching the other side, head back into Lasche Span, and remember to one zone a few times. An alternate way instead of using the mine cart is to zone back from Site 11 to Site 9, however, there is not a viable way to do this from Site 5. The Yagyu Darkblade is a 3/6/8/12% drop, so it may take a while, but remember that the chances of multiple drops increases with each jump in chain level.
One can use to their advantage the Zone Out Glitch to make chaining Bombshell and acquiring the Yagyu Darkblade faster.
The Yagyu Darkblade was named after Yagyū Munetoshi, a famous Japanese swordsman.