Chitinous Crawler is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of combat on your turn, choose target creature card in your graveyard. Conjure a duplicate of it into your graveyard. Descend 8 — Exile a permanent card from your graveyard: You may play it. Activate only as a sorcery and only if there are eight or more permanent cards in your graveyard.