Originally Posted by LicensedLuny

In PvE, go out with Charm Animal on your skillbar, and charm the level 5 version of the pet.

Go to the Zaishen Menagerie and show the level 5 pet to Emryd the Tamer. She will record the pet for your account's Menagerie. At this point, you can accept her offer to release the pet from your PvE character if you like.

Use a PvP-only caster character. Set it as Ranger secondary. Equip Charm Animal. To speed things up a little in the beginning, you can also equip some kind of health sacrifice skill. In the PvP Equipment screen, outfit this character with five superior runes and no health bonus runes. Create one weapon set of a Vampiric Axe (without a fortitude grip) and an offhand with the "Life is Pain!" inscription (without a focus core of fortitude.) This will be your suicide set. Create a second weapon set with any staff having a Hale Staff Head and a Staff Wrapping of Fortitude. Once you've leveled your pet, you will need to switch to this staff to be sure you have more than one hp and enough energy to use Charm Animal.

Use the two Mesmer heroes and one Necro hero. Set the Mesmers each with the following skill template.
- OQNDA8kdOmAPCDBNCAAAAAAA
Set the Necro with this skill template
- OANDQsNNPdi7QOBNCAAAAAAA
Make sure all heroes are set to Avoid Combat.

For the heroes equipment, outfit each of the Mesmers with a Fast Casting Staff using a Swift Staff Head and a "Don't Think Twice" inscription. Each Mesmer should also have a +1 Fast Casting mask with a superior Fast Casting rune. You can outfit the rest of their armor with Radiant Insignia and Runes of Attunement if you like, but it's not absolutely necessary. Outfit the Necro hero with a Blood Magic Staff using a Swift Staff Head, a "Don't Think Twice" inscription, and a Staff Wrapping of Enchanting. The Necro hero should have a +1 Blood Magic scar pattern (hat) with a superior Blood Magic Rune. Another piece of the Necro's armor should have at least a minor Soul Reaping rune. You can fill the rest of the Necro's armor with Survivor insignia and Vigor/Vitae runes, but it's not necessary.

With these three heroes, visit the Menagerie on your PvP caster. Find the level 5 versions of your pet on the grounds. Approach them and begin charming one, but cancel the charm before it finishes. The pet (and any copies of the same type nearby) will turn red/hostile when you begin charming, but it will not attack you or the heroes. If there is more than one copy of the pet nearby, they will share experience from your deaths. You can speed up the process of death leveling by killing all but one of the copies if you like.

Now disable your heroes' healing and res spells (hold Shift while clicking them on the hero's skill bar to toggle them as enabled or disabled,) and switch to your vampiric set. Let yourself die from the degen or hurry it along with a health sacrifice skill. After the first death, enable the heroes' res spells and one's healing spell. When they res you, switch out of your vamp set and heal up. This goes fastest if you have 30% Death Penalty, and you need to wait a few seconds before your second death to get to 30%. Notice the range the pet wanders, and try to flag your heroes in the center of this range. Stand with them and start suiciding again. You will res with 1 hp and immediately die again due to the vampiric axe's degen effect. Just let your heroes res you repeatedly. The pet gains experience each time you die.

It's fine to be afk while leveling. In about 20 min. or so, the pet will be level 20. Be ready to switch to your +60hp staff weapon slot. I find repeatedly pushing the weapon slot call key will get me switched before my 1hp drains off without too many tries. Now you can finish charming the level 20 pet. Once charmed, head back to the beginning of the Menagerie grounds and show Emryd your level 20 Hearty pet (yes, they even evolve Hearty so you get all the evolutions unlocked.)

Now you can take your PvE character(s) into the Menagerie and get Wynn to spawn charmable level 20 versions for you.