TC20 does not include HOTMs, Event or Season 2 heroes
The above google doc is very helpful.
Go to the hero page, filter the “Stars” column to 4 and 5, than the “Type of Hero” to 1st Release, 1.5 update and 1.8 update.
That should give you a list of 42 heroes
List
| Stars | Hero |
|---|---|
| ☆☆☆☆ | Boldtusk |
| ☆☆☆☆ | Boril |
| ☆☆☆☆ | Caedmon |
| ☆☆☆☆ | Chao |
| ☆☆☆☆ | Cyprian |
| ☆☆☆☆ | Little John |
| ☆☆☆☆ | Gormek |
| ☆☆☆☆ | Grimm |
| ☆☆☆☆ | Skittleskull |
| ☆☆☆☆ | Colen |
| ☆☆☆☆ | Kasshrek |
| ☆☆☆☆ | Kelile |
| ☆☆☆☆ | Kiril |
| ☆☆☆☆ | Li Xiu |
| ☆☆☆☆ | Melendor |
| ☆☆☆☆ | Rigard |
| ☆☆☆☆ | Sabina |
| ☆☆☆☆ | Scarlett |
| ☆☆☆☆ | Hu Tao |
| ☆☆☆☆ | Sonya |
| ☆☆☆☆ | Tiburtus |
| ☆☆☆☆ | Wu Kong |
| ☆☆☆☆☆ | Isarnia |
| ☆☆☆☆☆ | Domitia |
| ☆☆☆☆☆ | Elkanen |
| ☆☆☆☆☆ | Horghall |
| ☆☆☆☆☆ | Quintus |
| ☆☆☆☆☆ | Joon |
| ☆☆☆☆☆ | Azlar |
| ☆☆☆☆☆ | Kadilen |
| ☆☆☆☆☆ | Elena |
| ☆☆☆☆☆ | Leonidas |
| ☆☆☆☆☆ | Lianna |
| ☆☆☆☆☆ | Magni |
| ☆☆☆☆☆ | Marjana |
| ☆☆☆☆☆ | Obakan |
| ☆☆☆☆☆ | Khagan |
| ☆☆☆☆☆ | Richard |
| ☆☆☆☆☆ | Sartana |
| ☆☆☆☆☆ | Thorne |
| ☆☆☆☆☆ | Justice |
| ☆☆☆☆☆ | Vivica |