25 units, 20 Vanir and 5 Seraphim (Trap bonus +4.75 %, Elementary bonus +22.5 %), and I don't put my best gear in these guys, my fortress is level 16. My odds have risen from 50/50 to 70/30 aprox., that is the reason because I am happier now but TBH I've just realised that I have lost against you
Before, I was doing fights in easy and it was a sure victory but I was not getting elementals, so I tried medium fights instead, I lost a lot of fights at first but later I started to train Seraphim and my odds rose (i think i dissmissed two vanirs in the process)
I am only sure about how it works with elementals more or less, with a 25% you have a chance of 1/4 to get a elemental in easy mode (obviously) but 50% to get it in medium mode plus 12,5% to get two elementals, trying hard mode the odds to get a elemental should be amazing but I think that I will need a lot of Seraphim to have a chance