Please could someone explain to me how this event works? 

Somehow it doesn't make sense to me... 

Here are the official rewards for this event: 

Genbo Level 1-40 (epic hero)
Skullcrown  Level 41-50 (epic hero)
Goffred Brassclad Level 51-80 (legendary hero)
Teodor the Savant Level 81-100 (legendary hero)
 

Better heroes (Teodor the Savant is said to be one of the best heroes) are at lower ranks. 

So this means that to get a better reward, I must not try too hard to stay between 81 - 100 ? 

Or will I get rewards from all previous ranks when my rank is between 1 - 40?