That was an early version, in the mean time I modified it quite a lot. The firing mode currently charges up the vortex in four steps, each requiring 2 seconds charging. If you charge for less than 2 seconds, there won't be a vortex. The Nephthys just fires the smaller point singularity projectile that is also used for the primary fire mode. Very similar to the Paladin shot, except that it constantly attracts nearby objects (the vortex also does that before it really starts up) and releases electric discharges once in a while at nearby targets. The point singularity implodes on impact, giving everything around it a push towards the point of impact. The rate of fire is also a bit faster than that of the Paladin - 2 instead of 2.35 game seconds between shots.
Ok, back to the Gravity Vortex mode. If you charge for more than 2 seconds, you get the Gravity Vortex projectile. It has a start-up delay of 2 seconds, during which it acts a bit like the point singularity projectile - slightly attracting nearby objects and releasing electric discharges at nearby targets. Unlike the point singularity, the vortex is first affected by gravity to a certain extend, but when it starts up, it raises into the air a bit and finally comes to a stand-still. During its run time , it slightly increases its sucking radius and strength (you can see that effect in the video) until it finally collapses and explodes. (The final explosion effect is still missing.) The four charge levels correspond to 4, 6, 8 and 10 seconds of run time and also the initial sucking strength and radius. In addition to sucking in objects, the active vortex also zaps nearby objects and if anything is sucked in enough to touch the vortex, that causes a momentary gravity inversion. You can call it an explosion, if you want.

The real danger of the vortex are the touch explosions. If you just put a vortex next to a node or core, it will probably receive a lot less damage than you'd expect. However, if it is close enough and also sucks in stuff, it can do quite some damage to anything in range.
But as I mentioned, I am still tweaking it and what you saw in the video is stronger than the vortex is now. Also I found it to be quite hard to place the vortex exactly where I want it to be. So if you don't put nodes and cores in tights areas, it should be hard to use the maximum vortex effect against them.
In other news: The Nephthys also has a gunner seat now, which is a lightning turret that works much like the Lightning Gun with slightly higher rate of fire and damage amount.