The LEGO Batman Movie theme which was introduced in 2017 was based on The LEGO Batman Movie, a spin off of the The LEGO Movie featuring the Batman character. Sets in the theme were released in 2 waves.
2019 LEGO Sets
There were a number of events in 2019 that helped shaped the investment market for LEGO. Probably the most important event is that LEGO Star Wars celebrated its 20th anniversary. In addition, LEGO released new themes such as Hidden Side, Overwatch and a set based on the Netflix series Stranger Things. Sadly the Nexo Knights and Elves themes were discontinued in 2019.