Pests are typically harvested before they outgrow their enclosures. Blex is far from typical.

Blex, Vexing Pest

Other Pests, Bats, Insects, Snakes, and Spiders you control get +1/+1.
When Blex dies, you gain 4 life.

Search for Blex

Look at the top five cards of your library. You may put any number of them into your hand and the rest into your graveyard. You lose 3 life for each card you put into your hand this way.

Blex, Vexing Pest / Search for Blex

Blex, Vexing Pest / Search for Blex

Blex, Vexing Pest / Search for Blex

Blex, Vexing Pest / Search for Blex