That no advantage may be gained over us (ινα μη πλεονεκτηθωμεν). First aorist passive subjunctive after ινα μη (negative purpose) of πλεονεκτεω, old verb from πλεονεκτης, a covetous man (1 Corinthians 5:10), to take advantage of, to gain, to overreach. In N.T. only in 1 Thessalonians 4:6; 2 Corinthians 2:11; 2 Corinthians 7:2; 2 Corinthians 12:17. "That we may not be overreached by Satan."

His devices (αυτου τα νοηματα). Νοημα from νοεω to use the νους is old word, especially for evil plans and purposes as here.