If you disband the quest this item will still be in your inventory.
You can safely delete it.

Here's the original questline for all you nostalgics out there. Enjoy!

1. [48] Divine Retribution https://vanillawowdb.com/?quest=3441"">(Quest #3441)
2. [48] The Flawless Flame https://vanillawowdb.com/?quest=3442"">(Quest #3442)
3. [48] Forging the Shaft https://vanillawowdb.com/?quest=3443"">(Quest #3443)
4. [50] The Flame's Casing https://vanillawowdb.com/?quest=3452"">(Quest #3452)
5. [50] The Torch of Retribution https://vanillawowdb.com/?quest=3453"">(Quest #3453)
6. [50] The Torch of Retribution https://vanillawowdb.com/?quest=3454"">(Quest #3454)
7. [50] Squire Maltrake https://vanillawowdb.com/?quest=3462"">(Quest #3462)
8. [52] Set Them Ablaze! https://vanillawowdb.com/?quest=3463"">(Quest #3463)
9. [50] Trinkets... https://vanillawowdb.com/?quest=3481"">(Quest #3481)
10. [54] A Taste of Flame https://vanillawowdb.com/?quest=4023"">(Quest #4023)
11. [54] A Taste of Flame https://vanillawowdb.com/?quest=4022"">(Quest #4022)
12. [58D] A Taste of Flame https://vanillawowdb.com/?quest=4024"">(Quest #4024)

Please, rate this post up if you found it useful. Thank you! ;-)

I think it's worth noting that, even though the related quest has been removed from the game, if you still have this item in your inventory, you can still use it to gain the Encased Fiery Essence. Obviously there's nothing to do with that afterwards, but may make a decent conversation piece if you put it on your mantle :)