The former New Zealand Sportswoman of the Year was looking forward to spending more time at home with her family as she links up with her local team.
"I have thoroughly enjoyed my time playing for the Magic, which has been very special, but I'm really looking forward to a fresh challenge with the Pulse as I look to build my future closer to home," she said.
Van Dyk's acquisition has spelled the end of Australian import Caitlin Thwaites' time in the capital and she will likely return to play in Australia.
The Pulse have retained the services of coach Robyn Broughton for next season and once captain Katrina Grant inks a contract extension - which is a mere formality - the franchise will look to re-sign the majority of their roster from this season where they finished a franchise-best fifth.
Langman, who has played 90 tests and had played for the Magic for her entire professional career, said yesterday it was time for a change.
"I've had an amazing tenure at Magic and they will always be family for me, but I just feel it's the right time to try something new, open a new chapter in my netball career and give my all to the Mystics," she said.
Langman, 27, will be a useful cog in the Mystics' mid-court, while she will be joined in the side by Maria Tutaia, Kayla Cullen and Anna Harrison (maternity leave) who have all confirmed they will return to the Auckland-based franchise for next season.
The Mystics slumped to a woeful 1-12 record this year as they picked up the wooden spoon under interim coach Ruth Aitken but will be keen to rebound under the returning Debbie Fuller.
The Magic, meanwhile, will be desperate to hang on to defensive duo Leana de Bruin and Casey Kopua who are yet to announce plans for next year.
APNZ