It seems that many people including myself are having a problem with the Umbral flames quest where you have to defeat champions with Stasis damage.
The trick is that these champions only spawn in it in Nightfall ordeal Hero mode and for that you need 1220 light.
Another trick is that you must have your artifact upgraded that grants some of your weapons shield-piercing ability that is needed to take out the shield to kill those champions.
I hope this will be helpful and you will finish that quest needed for upgrading your stasis abilities.
▶️ 3Speak