Frozen - Into the Unknown
The Frozen - Into the Unknown event was first legendary event, and was released on May 27th, 2020. You will need Sven, Kristoff, Olaf, and Anna in order to unlock Elsa. Kristoff can be farmed in the club exchange as well as in the villains campaign, Anna can be farmed in the Tournament Exchange as well as in the villains campaign, and Sven and Olaf are farmable in the Grand Campaign.
This event will most likely return at the beginning of March.