Pursued by the Covenant , the Spartans retrieve the shard .
Pursued by the Covenant , the Spartans collapse the passage behind them , which saves them from the pursuing Covenant forces , but also traps them deep under the surface of Reach .
Pursued by the Covenant , the Spartans retrieve the shard and collapse the passage behind them , which saves them from the pursuing Covenant forces , but also traps them deep under the surface of Reach .