You need an Enhanced Ashes to Assets mod, which drops from Iron Banner packages (I got one) among other pinnacle activities, I believe. Then, you need a Telesto with at least four shots in it. The game thinks those Telesto bolts are enemies, so when you kill them all at once, voila, instant super, as seen in the video. This is an urgent problem because it works in both PvE and PvP, the latter being an imminent problem especially when Iron Banner is live. Update: Annnnd Telesto is now disabled.

Source: Forbes October 19, 2019 14:38 UTC