Until you can clear nightmare level on daily events (for the guaranteed 2 medals) consistently I would suggest to work on one hero per element for poison/ice/fire/magic (not metal because metal heroes are weak; so use the strongest of your others). Once you get there, you can start funnelling resources to 3
Until you are able to grind castles to get enough shards you’d generally be better off with the hero you get the free shard for, because that one is easier to star up. Afterwards, my preferences are
- Poison - Miasma; not useful for endless runs if you can reach 100+, but otherwise is good and the Level 20/50 bonuses are very good too.
- Ice - Arctor (although at some point you’d level Fursus for the bonus at level 50)
- Fire - Scorcher; is a bit of a liability for endless runs but for everything else Stress Shot is really powerful (much better than Wrath which adds `17% but only to your shots and Fiery Wings which adds 30% speed when jumping)
- Magic - still Hecate. I haven’t really compared with Prospero’s Magic bullets (they are not very powerful) and IMO Suppressive Fire is a little better than Decoy (although the magic bubble compensates for that somewhat - it’s based on a timer BTW), but currently you can’t star up Prospero without burning gems on banner summons