Alterra Mountain Co. has thrown down an $899 season pass that offers unlimited skiing at 12 resorts and a lower-cost version to replace the beloved Rocky Mountain SuperPass, promising a season-pass war that will challenge Vail Resorts’ previously unrivaled Epic Pass and transform the ski resort industry. The Ikon Pass — on sale March 6 at ikonpass.com — will offer unlimited access to Winter Park, Copper Mountain, Steamboat and Eldora and eight ski areas in California, Vermont, West Virginia and Canada, plus seven days of skiing each at six destination resorts: Utah’s Deer Valley, Wyoming’s Jackson Hole, Montana’s Big Sky, Canada’s Revelstoke, and Vermont’s Killington and Sugarbush.