How do you get rare heroes in AFK Arena?

I'm curious, could you elaborate on the strategies to acquire rare heroes in AFK Arena? As a player, I'm eager to expand my roster with powerful and unique characters. Do you recommend focusing on specific events, challenges, or game modes? Are there any in-game currencies or resources that I should prioritize for this purpose? Additionally, do you have any tips for maximizing my chances of obtaining these elusive heroes? I'm eager to learn more about the most effective methods for building a formidable team in AFK Arena.