Spirit of Summer: how to get the pet in WoW Forever
Spirit of Summer is a companion pet from Classic that returns in World of Warcraft: Forever. You learn it from 
Captured Flame.
In short
| Item | Captured Flame |
| Source | Quest: A Light in Dark Places |
| New in Forever | no, from Classic |
| Account-wide | yes, according to Wowhead |
How to get it
It is the reward of the quest A Light in Dark Places, from level 50, for both factions.
What changed since Classic
The item now teaches the pet: it becomes a spell and no longer takes a spot in your bags. Summoning it is instant instead of a 1 second cast, with a cooldown of 1.5 seconds.
Wowhead’s database marks the pet as account-wide: learned once, it would be there for every character. Blizzard has not confirmed that itself.
More pets from the same source
Every pet of WoW Forever, with where it comes from, is in the pet guide.
Frequently asked questions
How do you get Spirit of Summer in WoW Forever?
It is the reward of the quest A Light in Dark Places, from level 50, for both factions.
Is Spirit of Summer new in WoW Forever?
No. Spirit of Summer was already in Classic and returns in WoW Forever.
Sources: Wowhead