You can get free Avatars of Horizon Zero Dawn by watching some videos and visiting some webpages.

Quests you need to do and their rewards:

The Hunt Part 1
Reward: Exclusive Watcher Avatar!
– Watch “Countdown to Launch: Horizon Zero Dawn at PS Store” video
– Find out about our Facebook Event!
The Hunt Part 2
Reward: Exclusive Rost Avatar!
– Visit the Playlist Tab and Watch the “Horizon Zero Dawn – Story” trailer
– Available 2/21/17
So far, this is only available on the official US playstation website, but expect it to be rolled out globally soon.
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