PC Client from the Steam Steam Store
PC Client from the Official Wyvern Site
iOS Client from the Apple iOS App Store
Android Client from the Google Play Store
Wyvern subreddit is used by the community to discuss a variety of topics ranging from Patch Notes, to balancing, to memes.
Wyvern Source is an unofficial website very similar to Wyvern Wiki. It contains Wyvern related articles, quest guides, etc. Currently the site is no longer being updated. Please check Wyvern Wiki for the latest info.
Discord is used by the community to discuss a variety of topics ranging from Patch Notes, to balancing, to memes. Less serious and more troll version of Reddit.
Other Useful Links
How to create Custom Images for your character
fiverr: a site to hire pixel art designers to make your custom images
How Wyvern Accounts work (e.g. linking to Steam, iOS, Android)