Legacy explained: 65 challenges, one point each, 16 points per character, no alt required

The Legacy system unlocks with your first point (level 25, a 150 non-gathering tradeskill, or exploring the whole map). Sixty-five challenges in six categories give one point each, account-wide for non-Hardcore characters. Each character spends up to 16 in Professions, Adventure and Resourcefulness. One character can earn 29 points alone, which is why the cap exists: new players catch up and alts stay optional.

The reward track has four cosmetic rewards at launch. Hardcore will get twelve challenges of its own, and challenges earned there count everywhere.

Sources

• Blizzard: Get to Know the Legacy System
• Legacy planner