Remain Lights

Remain Lights (リメインライト), in ALfheim Online, are the leftover souls of killed players that remain in the place that they were killed in for about 1 minute. During this time, the player can be revived on the spot with revive magic or items. If the player isn't revived before the timer expires, the Light vanishes and the player is returned to one's re-spawn point. Though dead players aren't able to move or take any action while they are dead, they can still hear and see what is going on around them.

Colors
The color of the Remain Light's flame is different for each race, based on their primary color:

Fairy Dance Arc
After Kirito skewers two Salamanders, they go up in flames, which are the Remain Lights. Their souls, after disappearing, go back to their city, where they restart their journey.

They are also present when General Eugene is killed by Kirito in their duel, and later revived by Sakuya.

When Kirito attempts to clear the Grand Quest to climb the Yggdrasil, the World Tree, he is defeated by an onslaught of Guardian Archers. At this point, his Remain Light can be seen for the first time.

Trivia

 * Although the death timer is usually only 1 minute in a neutral area, the timer increases to 600 seconds (10 minutes) within a boss room or certain dungeons.

Reference
Luz de permanencia Remain Light Посмертный огонь