Final answer:
The statement implies a sense of unity and foreshadows betrayal. The literary element being used is foreshadowing.
Step-by-step explanation:
The statement implies a sense of unity and foreshadows betrayal. The literary element being used is foreshadowing. By stating that Heorot was filled with friends and that no Scylding folk had attempted treachery, the author creates the expectation that treachery might occur in the future.