The reason you died is likely that you were stuck somewhere where you couldn't attack... so after so many hours of 1 dmg you eventually died.
You can get the butterfly pet as well the books. They are two different quests you get from killing 40k mobs.
One of them is the Drifting Book quest which gets you the book with the hamster on top. You can repeat this quest every week. You will need to be in a party with 2 other people with the title Entomologist and the party leader will talk to the tower. Wait 10 min and you'll get a pet.
The other quest is the Insect Kindergarten. You will receive 10 free Hatcheries daily for the pet you will receive at the end (ie. Butterfly Hatchery for the Butterfly pet). The hatchery requires you to kill 100 mobs of any type and it'll turn into a toy for the pet. Repeat this 10 times to get an egg... the egg then requires you to stay online for a total of 24 hrs. After all that you will receive the Butterfly pet.
Picture of pets:
Chrysalis
Grub
Threaded Mode