It seems that this problem pops up again everytime the Corrupted Strike is in the Nightfall Playlist. So, here's a quick guide for New Light [i](new Players)[/i] that haven't figure it out yet. When you'll reach Seda, the Boss, you'll immediately notice that she is invulnerable. You can't damage her, you have to remove her Shield first. To do so, pick up the glowing Sphere on the side platform, the one on the small pedestal. By pressing the Trigger/Shot Button, you'll throw it. You have to it her with that Sphere to remove her shield. You can also throw the sphere to another Guardian. If the Guardian is facing you, the Sphere will be passed and empowered causing more damage to her and the shield. This is particulary usefull on the Nightfall where you might need two regular Spheres to remove her shield. In this way, you'll only need one. In the final part of the Boss Fight the mechanic works the same way. Pick up the Sphere and throw it to her to remove the shield, or pass it to another Guardian first to empowered it, then throw. The Sphere has a quite nice auto-track, but it's not infallible. You must aim at her before throw it to be sure to hit. You can also press the ADS button to aim better. The Sphere can also be used against regular enemies to damage them, but it's not really that powerful. Hope this may help!