Simon Dean took charge after ministers put Betsi Cadwaladr University Health Board in special measures amid concerns about management failings.
A report also condemned poor treatment of mental health patients at Glan Clwyd Hospital as "institutional abuse".
Mr Dean said his priority was to "get out and about and listen to people".
Meeting families of patients on the Tawel Fan mental health ward had been a "powerful and humbling experience", he said.
The deputy chief executive of the Wales NHS was asked by Health Minister Mark Drakeford to run Wales' largest health board following the suspension of its chief executive Trevor Purt earlier in June.
Mr Dean said he did not know how long he would be in charge as he sought to provide "stability and leadership".
"I don't see myself as the saviour of Betsi. This is a team effort. I see my role as being a catalyst," he said.
The 100-day plans will set out objectives and milestones, but that does not mean everything will be resolved in that time, he added.
Mr Dean said people would be held to account where it was required.
"We have to see special measures as an opportunity rather than a challenge. I am very heartened by the way staff have responded," he said.
The man given the job of running the NHS in north Wales has asked staff for 100-day plans to turn the region's troubled health service around.