Defeat the Fist of Crota leading the Spawn in the Cosmodrome.
“ The Spawn will follow the Fist, while the Will grows Crota’s army. I’ve seen this all before. “ - Eris.
Speak with Eris at the Tower and accept this quest. Choose this mission on Earth and you’ll land in The Blast. Omnigul, the Will of Crota, will be here as well as many Fallen. Take out the enemies with their backs to you to thin the numbers overall then be ready for the Thrall to charge you. Omnigul will summon Cursed Thrall for you to defeat; once cleared, the Will of Crota will leave allowing you passage into the tunnels.
As you make your way into the Refinery you’ll encounter a Blade of Crota , a tough Knight that will drop it’s blade once defeated. Use the Blade of Crota to clear out the Thrall and Acolytes ahead then enter the tunnel to The Grottos where you’ll encounter a restricted zone.
Sardon, Fist of Crota
Approach the floating light in the middle of The Grottos to spawn Sardon. He is fast and wields a powerful blade; you’re also afflicted with “A Dark Burden” that slows you and limits your jumping ability which makes it difficult to keep your distance. Use a Fusion Rifle/Shotgun and a Hand Cannon to deal high damage quickly and toss Grenades when you have a clear shot. The Grenade should cause Sardon to flinch and set up nicely for some Rocket Launcher shots, allowing you to quickly burn through Sardon’s health. Once completed you’ll receive your rewards and a Shard of the Fist’s Blade .
“ The Fist has fallen, but the Spawn of Crota still infect these lands. “ - Eris
“ My fears appear to be true, this could be the beginning of a dark journey. “ - Eris