Grandmaster Ninja is the Tier 5 upgrade of Path 1 for the Ninja Monkey in Bloons TD 6. It is a much more powerful version of Bloonjitsu that shoots much faster (specifically one shot every 0.217s), gains +10 range, deals greater damage (2 per shuriken instead of 1, but not for Caltrops), and throws 8 shurikens per shot (9 with the Deadly Tranquility MK) instead of 5.
Grandmaster Ninja is a powerful Ninja Monkey upgrade that is highly dependent on numerous external buffs in order to maximize its efficiency. To maximize its power, buffs from up to 20 Shinobi Tactics, continuous Overclock, and a nearby Stronger Stimulant are necessary, along with a hero such as Level 11+ Obyn or Level 3+ Pat Fusty. With Seeking Shuriken, a highly buffed Grandmaster Ninja excels at hitting large numbers of bloons rather quickly and accurately.
It is very well advised to spam Shinobi Tactics Ninjas around the Grandmaster Ninja to maximise its bloon shredding power.
When choosing crosspaths for the Grandmaster Ninja, it is best to choose Path 3 upgrades (Seeking Shuriken and Caltrops) for increased DPS output, allowing the fast powerful shurikens to hit targets more often. Path 2 upgrades (Distraction and Counter-Espionage) give Grandmaster an okay support option. But for most situations, Path 3 is superior, provided there is a Shinobi Tactics army around the Grandmaster Ninja, as such an army already provides Path 2 benefits anyways.
With the Deadly Tranquility Monkey Knowledge, the Grandmaster Ninja throws 9 shurikens, further increasing its power.
Note that it still cannot pop Lead Bloons, so it's advised to add some towers that can pop leads and/or DDTs, or even give the Grandmaster Ninja lead-popping power.
The only three ways to give the Ninja lead-popping power are through Monkey Intelligence Bureau, Acidic Mixture Dip, or Heat It Up (from Gwendolin's support). Usually, MIB would be needed, especially on short maps, as Heat It Up and Acidic Mixture Dip aren't reliable enough on their own to give Grandmaster with the needed lead-popping power (except with permabrew).
Because a Grandmaster Ninja attacks quite quickly, it may wear out Stronger Stimulant buffs quite fast, though the Version 13.0 rework to the Grandmaster Ninja means a plain Grandmaster Ninja can sustain an Alch buff for longer.
While Stronger Stimulant gives the Grandmaster Ninja a short-lived boost in DPS, especially when paired with a multitude of attack speed buffs, Permanent Brew will allow him to consistently pop Lead and quadruple his damage against MOAB-Class bloons while also increasing his range. Plus, this will also improve any nearby Shinobi Tactics for even more stat boosts.
As of Version 13.0, Stronger Stimulant has almost full uptime on a plain Grandmaster Ninja due to to an attack speed decrease.
The Grandmaster Ninja attack speed is about 2 times faster than Ninja Discipline or roughly 3 times faster than the base tower.
Grandmaster Ninja gained a pierce buff in Version 9.0 due to its former inefficiency compared to multiple Bloonjitsus, ignoring physical space. However, Version 11.0 buffed Shinobi Tactics to also provide nearby Ninjas with bonus pierce, which further boosted Grandmaster Ninja. In Version 13.0, Grandmaster Ninja was reworked to synergize less when combined with stat bonuses such as Alch buff, Shinobi spam, and Pat Fusty's Rallying Roar. It still remains a viable option on CHIMPS strategy when paired with Shinobi spam and Pat Fusty's Rallying Roar.
Grandmaster Ninja has +2 pierce for all attacks.
Grandmaster Ninja damage increased from 1 to 2
Grandmaster Ninja attack rate reduced from 0.1 to 0.217
Grandmaster Ninja pierce reduced from 6 to 4
As ninja is the ‘Camo Specialist' and has been since inception, it is the only tower that will unlock Camo Prioritization on the base tower. [...]
This has been used in two different Two Towers CHIMPS combos, with Permanent Brew (now impossible after Grandmaster's nerf in Version 13.0) and Wizard Lord Phoenix (Main hard Round was 100, wasn't beaten until 11.0 because there wasn't enough DPS against the BAD; also was the first combo completed on Version 11.0).
The damage buff that the Grandmaster Ninja receives does not affect the Caltrops attack from the 5-0-2 crosspath. In addition, there is a bug where the caltrops have 5 pierce instead of 6 despite attacking at the same base rate of 4.4s.