What I need for Next League in Soulkeep?

I am enjoying soulkeep to much and this is not just in words but actually I spend Credits and rent cards more than I did in Splinterlands and I do not expect that and In this day I wanted to check leagues icon to see what I will get and as you can see I have some info to share with you.

I am now in level 4 and I though it is about levels to be in the next league but as I have read it is about fiends souls that you have eliminated and as you can see I have collected 622 common fiends and need more than 1500 and for rare I have killed 124 and still needs about 300 and for epic I have killed 17 out of 38.

Still confused about this but if this true I have a long way still as I have remembered in first level there was too small amount of fiends and in level 2 as well, The only level that was so hard and I have killed so many fiends was level 3 that mean level 4 and 5 will be much harder and I need to be prepared well to be able to kill these amount of fiends that are remaining.

There also one thing that confirmed to me that I will use level 1 cards in this league even if I rent a level 10 cards and the only exception to use level 2 card is to use epic one and also for legendary.

One thing that pleased me and motivate me to complete and pass the remaining levels is that no legendary fiend I have killed and no one will face me in the next levels and epic amount also not much this means there will be huge amount of common fiends that will need high fire rate and more towers and spells.