The chances of getting a castle key in a hard/nightmare daily event are as follows:
| Keys | Chance |
|---|---|
| 0 | 69.51% (~7 in 10) |
| 1 | 25.54% (~1 in 4) |
| 2 | 4.43% (~1 in 23) |
| 3 | ~1 in 200 |
| 4 | ~1 in 2,700 |
| 5 | ~1 in 50,000 |
| 6 | ~1 in 1,000,000 |
If we consider the chances of streaks of 0 keys;
| Completed runs with 0 keys | Chance |
|---|---|
| 1 run | ~70% |
| 2 runs | ~48% |
| 3 runs | ~34% |
| 4 runs | ~23% |
| 5 runs | ~16% |
| 6 runs | ~11% |
| 7 runs | ~8% |
| 8 runs | ~5% |
| 9 runs | ~4% |
| 10 runs | ~3% |
| 11 runs | ~2% |
| 12 runs | ~1% |
So if we take any particular time interval covering 12 runs, about 1 % of players will have 0 keys