Get a guaranteed 2,000 points after two stays, a targeted bonus after that. Register between now and 31 December 2019 and stay between 29 October to 14 January 2020.
It's not strictly speaking a 100,000 miles bonus, but it's still a way to pick up miles for cheap...assuming you've got some really big spending planned.
The Conrad Seoul is definitely one of the better hotels I have stayed in. Great executive lounge, nice breakfast spread, and a huge gym to work all that food off. Pity about its location though.