Wyvern

The Wyvern is a creature that spawns on the same hight as harpies and near floating islands in hard mode(after killing wall of flesh). The Wavern can be hard to defeat without the right strategy. Wavern drops soul of flight upon death. The soul of flight can be used to make angel and demon wings along with feathers that are dropped by harpies. Due to harpies attacking along with wavern he can be a difficult enemy. Using the right startegy can eliminate this factor.

Strategy
Build a skybridge as shown in the video and use a repeater or minishark to shoot him while using the skybridge as platform to dodge his attacks.Stand still in between attacks so that he comes down vertically and shoot to do full body damage. Another interesting strategy was discussed in the Terraria wiki: Make a sky bridge in the atmosphere (where gravity has less effect.) Use at least ~300 blocks so you can do a full run, jump, and float with Spectre Boots & Cloud in a Balloon twice. Build either Cobalt Repeater or Mythril Repeater, Cobalt Armor with magic buff and craft Crystal Storm. Then run fast so the Wyvern follows you in a more or less straight line, shooting him with Crystal Storm along his length until you're out of mana, then switch to the repeater (I used Jester's Arrows) Once your mana is full again, switch back. If you reach the end of your bridge, turn around and run the other way. Using the atmosphere this way makes it easier to dodge the Wyvern's attacks. Another means of killing him easily is to have your star cannon, and around 10 - 20 fallen stars. Run so that he is following you, then shoot the stars through his body. With around 5 stars, I was able to halve his health. So depending on your accuracy, 10 - 20 stars should do it.