By Fire Be... Merged?

Super easy to complete using [item=119093] and/or Goblin Glider Kit Simply use the feather to gain some altitude and fly back down to Firaga.

Since I haven't seen it mentioned yet: you DO need to be on Assault on Magnarok/Assault on Magnarok to pick up the quest for this achievement.

I had the daily and did That Was Entirely Unnecessary first, and ended up completing it in the process. When I found [npc=87971], it had no quest for me. After abandoning the daily, and then re-accepting it, I was able to pick up Rekindling an Old Flame and get my achievement.

I used [item=119093] to gain some height, clicked off the buff and when I was close to the ground used my Goblin Glider Kit.

Firaga is a fire elemental at the back of Magnarok near the water (coords 75, 30). To get this acheivement, you need to pick up the Essence of Flame and carry it to Firaga without mounting or getting hit by the tornadoes, and without reigniting it on the pyres. I didn't aggro anything, so I'm not sure if combat causes you to drop it. I'm a rogue, so i just stealthed and sprinted to him.