He knows how to bide his time and never casually reveals his real strength.
Tips
history
From 《旧唐书·宣宗记》: '愈事韬晦,群居游处,未尝有言' — the future Emperor Xuanzong concealed his abilities before taking the throne, living quietly and speaking little. 韬 = 'sheathe,' 晦 = 'darken' — to sheathe one's light.
culture
Famously associated with Deng Xiaoping's (邓小平) 1990s foreign-policy guideline '韬光养晦,有所作为' — 'keep a low profile; accomplish something.' For years it shaped China's measured international posture; the phrase still appears in policy commentary.