Temple Raid portraits are available to those who are able to defeat all of the Guardians in the Shrine of the Guardians.
Players will receive the first tier guardian portrait for defeating all of the Orange Tier Guardians. Those who are able to defeat the Harbinger Tier Guardians will receive both the first tier and Uber (second tier) portrait.
Please be aware that there is a delay between when you defeat the guardians and when the portrait(s) will unlock on your account.
Each run of the event will have a different Guardian portrait available for players to unlock, so keep an eye out for which will be available!