Where can I find a complete list of all heroes (rarity + availability)?

[Karin]

Is it impossible to find characters that not listed in this forum or fandom? Like 3 star mythics that given before 2019, etc.

There is some gap between the time when the wiki stopped, around 2016 I think, and the forum changed platform in 2018 and not all the old posts were moved. The heroes that were released as prizes and in special packs during that time are not listed anywhere.