Wyvern

A Wyvern is a flying, non-solid enemy, added and only available in the 1.1 update and after. It slightly resembles the face of a dog and the body of a serpent/dragon with hands and feet.

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It has a total of 4,000 health, and will only spawn after the player has defeated the Wall of Flesh when the player is at sky level, which varies based on the size of the world. On small worlds, this is anywhere above 300 feet high. On normal worlds, this is anywhere above 500 feet high. And on large worlds, this is anywhere over 1000 feet high. Anyplace high enough to spawn a Harpy is also high enough to spawn a Wyvern. It seems to spawn lower than this on blood moons. This enemy is a mini boss, and can be dangerous for players not wearing good armor, as the head can hit an undefended player up to 90 damage, while the body only does about 40. This is still dangerous because the Wyvern tends to charge into you, and lingering in one spot while it is hitting you can rack up a lot of damage.

Option 1
A good strategy will be to make 2 wide platforms out of Wood Platforms, one above the other, and when the Wyvern appears, stand on the lower platform and just move left and right a little. Time your jump to the moment the head almost touches you. You should dodge its attacks most of the time.

Option 2
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 (Recommended with 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. The Minishark or Megashark also works in this situation. Make sure it has a higher-powered bullet, (Such as the Crystal Bullet which breaks into 3 seperate bullet causing additional damage.) Ironskin and Health regeneration potions are recommended and 400/400 health is ideal. Additionally, if you have the means, you can also use a Demon Scythe the same way you would as with the Star Cannon. Since the Demon Scythe hits five times before disappearing, this can easily take down over 1000 health in one pass, though it will wear down about half of your mana.

Option 3
With rocket boots, spectre boots, or wings, you can go in a repetitive motion of jumping and flying to the right, attack from above,and wait for him to come back into sight, then fly left, attack from above, and wait for him to come back into sight, and repeat this. By doing this he will continue to fly in this repetitive motion of back and forth, while you attack from above. I have also learned that using a Grenade works very well since all the segments of his body can take damage. A Grenade will be able to hit up to 6 segments of his body because of the explosion, but usually hits about 4. Still this method is extremely useful. The Flamethrower is also a good option, although this does not do damage to more than one section, if you fire it at 90 degrees to his body as he passes, a lot of damage will be done.

Option 4
Get a relatively powerful flail, (Sunfury, or if you're wanting top tier gear, a Dao of Pow ) Use a gravitation potion until it spawns, immediately use the gravity to your advantage and flip directly downwards (don't move, just make sure you're moving vertically constantly) the Wyvern will still catch up to you (recommended medium world or higher) and aim directly up with the flail when it gets near. With a Dao of Pow, you can take at least 1000+health off this creature per swing.

Option 5
Buy the Ice Rod, cast it under you while jumping up, (Works better with Rocket Boots and a Cloud in a Bottle, or other jumping items). Get the Wyvern's attention and jump back down, cast Demon Scythe going up, and keep casting it, and it will hit the Wyvern while you are falling down, then finish the battle on the ground level, Normally the Wyvern will have 1000/4000 HP left. Doing this on a large map is ideal, as it is possible to kill it before you reach the ground. Though keep in mind that the souls it drops (Souls of Flight) aren't affected by gravity, so waiting until you're just above ground and then cast the final demon scythe will make it easier to obtain the souls.

Option 6
Make a couple of gravitation potions, float to the very top of the world above your spawn. There will be a large amount of Harpies, but dodge their shots while taking them out with a ranged weapon of choice. Then, as the Wyvern appears, drop to the ground. The Wyvern will head directly towards you, slightly faster than you are. Use the Mini/Megashark to shoot straight down it, as it will hit every link. As it is about to hit you, move to the side and it will continue a ways and come back at you. Continue the fight by changing gravity to avoid it's attacks, and it shouldn't take long as the intial drop should have lowered it's health a lot. If need be, you should be close to your spawn to heal.

Option 7
You will need either a Magical Harp or a Demon Scythe, and some mana potions for this to work. Get to the top of the world with a gravitation potion and wait for Wyvern to spawn. as soon as he spawns, start killing him with your weapon, pausing only to heal/restore mana. Go up to the top of the world when you reach the ground, then back down when you reach the top, spreading the damage with your weapon until it dies.

Option 8
Use a Spear weapon, like a Mythril Halberd, to run a long distance until the wyvern is completely horizontal. After that, remain running and wait until it almost catches up with you.(Hermes Boots are recommended) When it is about 4 blocks behind you, attack it with the halberd. With a single thrust, you can do about 600 hp of damage. When it is about to hit you, simply jump upwards and the wyvern will fly past you harmlessly. Note that this strategy is extremly risky and good armor is recommended, along with healing potions.

Option 9
(please note that this only works on slower computers and it involves the exploitation of a glitch that does not work in every case) You will need to run an energy-consuming program at the same time as Terraria (for mac, quicktime is recommended). This will hopefully slow down the speed of terraria. You can see if it worked by drinking a healing potion and seeing if the cooldown timer is in real time. If it works, then simply go up to the top of the atmosphere, and wait for a wyvern to arrive. This can be sped up using a water candle. It will attack you in large, slow loops. Wait till the last second as it approaches and jump over it with rocket boots or wings and shoot down at it with any ranged weapon or mace, and repeat. The point of slowing down Terraria is that it gives you more time to jump out of the way before the Wyvern hits you. It is recommended that you have atleast 30 defence before trying this. One simple way is with full molten armor and a minishark with about 700 silver bullets.

Option 10
For this you will need a pair of wings, either angel or demon, a floating island, and a flame thrower. Go all the way on top of the floating island, wait until the Wyvern spawns and make sure its coming head on at you. Then jump off the island, the Wyvern should be charging at you and you should be completely parrell to it. Aim your flame thrower at its head and fire away, this should keep doing damage to the Wyvern. Fly all the way up and repeat till the Wyvern is dead. (should take 2 or 3 times.) This is a safe way where you take very few damange and finish the Wyvern fast.

Option 11

Build a house for the nurse away from other npc's. Summon the Wvyren, and stand right above where the nurse is, making sure you can still talk to her. The Wvyren will do a figure of 8 to hit you (when standing still), so use something like the Dao of Pow, and just hold it, healing with the nurse whenever you're health is low.

Bugs

 * Sometimes, if a Wyvern is killed in multiplayer when it's laggy, it's head will stay and keep attacking you.
 * There's a glitch where there can be more than 1 at a time.
 * There is a rare glitch in which the Wyvern has a tail of the Bone Serpent.
 * Wyverns may get knocked back a little bit when hit by an attack in laggy multiplayer servers.

Tips

 * Since the damage the head does is much higher than the body, it's best to try and avoid it, even if it means having to touch its body.
 * It can follow you down to the ground.
 * Using the Dao of Pow can be extremely effective, however like any burrowing enemy, it cannot be confused.
 * Using Ranged weapons can be much more effective than melee. Good weapons would be the Starfury, the Starcannon, the Shotgun, any Repeater or the Megashark.
 * If you have a Demon Scythe, Water Bolt or Magical Harp, it may take very high damage if lined-up with projectiles trajectory.
 * You can also build a tall tower up from your spawn to aggro a Wyvern, then use the Magic Mirror to teleport down and hopefully have the Wyvern follow you. You can use a nurse at your house for this to make it even easier to win.
 * For first timers, it would be wise to go against this enemy in singleplayer to get used to its pattern.
 * If you die, they appear to automatically regenerate health back to 4000.
 * A Wyvern is able to follow you to your home as it can fly faster than you even if you're wearing Hermes Boots. Do not run away and go back to your home as it may catch you by suprise.
 * The Wyvern has a long body, which can be turned to your advantage by building a small room and using attacks that ricochet off walls (Cursed Flame, Crystal Storm, Light Disk...etc.) inside. As the Wyvern charges through, it will be hit by each projectile multiple times, increase your damage potential.
 * Using a spear, if available, is recommended do to a spear being able to strike in any degree angle of your character as well as damaging the wyvern multiple times in a single attack
 * With the right equipment and line of fire, the Magical Harp can kill him with 6 shots.
 * If you build a small house at the top of the world, with a bed inside, you can set it as your warp point for the magic mirror. After the wyvern attacks you, you can simply jump off and strike him all the way down. If this doesn't kill it, just magic mirror back up to the top, and start over.