10
Dropped by
the missile is not the weapon
The projectile itself does nothing on contact. What matters is the ball of electricity it leaves behind at the point of impact, which sits in place and ticks away at whatever wanders into it. That flips how you aim: you are placing a field on the ground or against a wall where the enemy is going to be, not trying to hit them directly. Against something stationary or slow it is excellent, and against a fast boss that never returns to the same spot it is close to useless.
only one field at a time
Firing again does not build a second field, it just moves the one you had. Spamming the trigger actively wastes your own damage. Fire, let it run its course, and only replace it when the target has left. The ticks also consume shared invincibility frames, so running this next to another rapid hitting weapon means the two of them are fighting over the same target.
what to load it with
The rocket sets the damage and nothing else carries over, so the variants that blow holes in terrain give you no explosion and no terrain damage here. Buy whichever tier gives you the damage you want and ignore the rest of the description.