Legend, Master and Grandmaster, compared
Nightfalls are three-player strikes with a difficulty dial, and the three rungs are genuinely different activities rather than the same strike with more health. Legend is a clean run at enhanced loot rates — the tier most players farm for weekly weapons. Master raises enemy density, adds champions and typically forces Match Game, so shield elements start dictating your loadout. Grandmaster is the wall: Contest Mode permanently caps you 25 power below the enemies no matter how high you actually are, revives are limited so a few careless deaths end the run outright, and the modifier stack is unforgiving.
That's why a GM is a coordination test, not a gear check — you can't simply out-level it. The practical consequences are anti-champion mods matched to the week's champion types, matching elemental damage for Match Game, and disciplined revive economy. Which specific strike is in rotation matters too: some GMs are short and efficient while others have multiple hard wipe points, so completion time swings widely week to week and we set expectations against the current rotation rather than promising a fixed clock.