Become Sentry is the fifteenth powerup in Fortress Blast. It was added to Fortress Blast in version 4.3 and is an entirely original powerup.
Become Sentry can only be used while a player is standing on the ground. Once this condition is met and the powerup is used, the user's model will disappear and be replaced by a Level 3 Sentry, freezing the user in place. This Sentry rotates and shoots autonomously as a normal Sentry would. At any time the user may press the jump or primary attack key, which will cause the Sentry to be destroyed and the player will regain control of their model. The only time that a player may not exit a Sentry is while it is being sapped, yet they will automatically exit it when it dies.
The resulting Sentry's health is independent of its parent player's original health. For example, if a player was to become a Sentry at half health the Sentry would spawn at full health, and no matter how much damage the Sentry takes that same player will always exit it at half health.