Demas was a trusted member of the apostle Paul’s ministry team. Paul said of him, “Epaphras, my fellow prisoner greets you, as do Mark, Aristarchus, Demas, Luke, my fellow laborers” (Philemon 23-24). Demas is even mentioned before Luke, author of Luke and Acts! Paul mentions him again in Col 4:14, also in a positive light.
About five years later (65-66 A.D.), shortly before he was martyred, Paul wrote 2 Timothy. In that letter he had bad news about Demas