Eggs, hatchlings, and adult dragons can all be killed. To attempt to kill a dragon, select the "Kill" option on its action page.
Killing an Egg
A dead egg
A killed egg appears as the jagged bottom half of an egg. Dead eggs remain on the scroll on which they died for two weeks. Killed eggs count as alive eggs (and thus are capable of locking a scroll) for 24 hours, so typically it is preferable to abandon an egg rather than killing it.
The message that one sees when successfully killing an egg, is as follows: "You take the egg and smash it on the ground, killing whatever was forming inside."
Killing a Hatchling
A dead hatchling or adult
Once a hatchling becomes a dragon, it becomes harder to kill as it will occasionally evade the blade. If this happens, a player cannot attempt to kill the hatchling again for another twenty-four hours. Dead hatchlings appear as tombstones and count as alive hatchlings for 24 hours. Sometimes you can use a magic spell to revive the hatchling. On rare occasions, reviving a hatchling or dragon will create a Zombie Dragon.
Eggs and hatchlings that have recently died or were killed can be found in the Graveyard
The message that one sees when successfully killing an (unnamed) hatchling, is as follows: "You take your deathnote and write the hatchling's name, watching the life slowly leave its eyes as it stares at you, wondering why you betrayed it."
Killing an Adult Dragon
Adult dragons can be very difficult to kill, meaning that they can be very prone to dodging your blade ("Dodgers" cannot be killed for 24 hours after a dodged kill attempt; they will continue to dodge the blade). Because of this, most players who no longer wish to have a certain adult on their scroll release that dragon to the wilderness instead of trying to kill it. Additionally, like all other stages of growth, the tombstone resulting from a dragon's death remains on the scroll for two weeks. Like hatchlings, a revive can be attempted and on rare occasions it will create a Zombie Dragon.
The message that one sees when successfully killing an (unnamed) adult dragon, is as follows: "You take your deathnote and write the dragon's name, watching the life slowly leave its eyes as it stares at you, wondering why you betrayed it."
Killing Cooldown
You can kill 5 dragons, hatchlings or eggs within a week. The unsuccessful vampire's bite is considered killing. The death of egg or a hatchling from illness or negligence isn't considered killing.
There is a confidential possibility to kill 6 dragons (one over a limit). For this purpose, after killing of a four, it is necessary to open dialogue for killing at once a two in different windows of the browser. It is not known, whether is it an bug of a cave or undocumented possibility (like shallow-water dragons' STRUGGLE).