Heart of a Champion
Quest reward from We Stand United. From what I can gather from information here on Wowhead, the quest this toy comes from is the same quest that rewards the rank 4 (legendary) version of the Crucible of Flame essence.
The 
Heart of a Champion is a Battle for Azeroth toy rewarded from the quest We Stand United, obtained after reaching neck level 70 on your Heart of Azeroth and completing the Rank 4 Crucible of Flame quest chain from Kalegos in the Chamber of the Heart.
Guide awaiting review
Reach Neck Level 70
You must reach level 70 on your Heart of Azeroth necklace before the quest chain that rewards this toy becomes available.
Accept Quest from Kalegos
Head to the Chamber of the Heart and accept the quest A Bolt from the Blue from Kalegos, which is the Rank 4 Crucible of Flame quest.
Complete A Bolt from the Blue
Complete the quest A Bolt from the Blue and return to the Chamber of the Heart.
Accept We Stand United
Magni Bronzebeard will offer you the quest We Stand United in the Chamber of the Heart, including a short cinematic of the dragonflights empowering the Heart of Azeroth. Complete the quest to receive the Heart of a Champion toy.
