Glaives is an upgrade for the Boomerang Thrower, which allows the Boomerang Thrower to Throw Glaives instead of Boomerangs. Glaives are capable of popping up to 8 Bloons at a time in Bloons TD 3 and up to 12 Bloons at a time in Bloons TD 4 and Bloons TD 5. It is the Boomerang Thrower's third upgrade in Bloons TD 4 and second upgrade on the first path in Bloons TD 5. In Bloons TD 5, it costs $240 on Easy, $280 on Medium, $300 on Hard and $335 on Impoppable. Glaives also provide a slight increase in throwing speed.
In Bloons TD 6, this upgrade makes a return under the name Glaives. Glaives increases the Boomerang Monkey's Pierce to 13 (from 8). It is the second upgrade on the first path and can be unlocked for 520 XP. In BTD6, this upgrade also increases the attack speed of the tower from about 1.42 seconds per shot to 1.2 seconds per shot.