Blizzard is joining the stay at home promotion on several fronts. Besides offering experience boost in World of Warcraft, they are also offering all Heroes of the Storm characters for free to try but not to keep, until 2 April 2020.
Blizzard's MOBA, Heroes of the Storm may not be as popular as League of Legends or Dota 2 but it has a dedicated player base. Blizzard somewhat recently gave up the game's esports scene but they are still organising certain events from time to time.
Considering the situation in the world, it is not particularly odd that they added a two-week event for everyone where all the heroes become available. Still, none of the heroes are free to keep and will need to be unlocked the good old fashioned way.
On the other hand, this is the perfect time to try them out, especially the ones that may have caught your eye but you weren't quite set on. Maybe trying them out will help you get off the fence, in either direction.
There are 88 heroes in total to choose from which is quite the time-consuming roster to try out. Even the newest addition, Deathwing, will be free during this period. Considering it's not entirely clear how he fits so far, this may be the perfect time to see the dragon's synergies and counters.
Heroes of the Storm is also free to play so there is nothing to stop you from trying the game out for the time being, especially if you are not too keen on the classic MOBA formats.