Let's come up with an amphibian race!

Regarding the crocodiles, let's say the chance of them biting is 20 percent. This will work if the number of crocodiles is equal to or greater than the number of units they are attacking, but not less. Maybe that's the way to go... Also, what will be the name of this unit? "Crocodile" doesn't sound very good; it's better to come up with something else.

No, we need to think of something else; this option is unlikely to work because the crocodiles will be like the Garagon in Might and Magic III, but 100 times more effective. The bite chance should depend not only on the number but also on the level, because there will always be more than 5, 6, or 7 troops, and they will be the ones suffering.
I wrote to Andrei in a private message to make the bite chance some percentage, and the number of "bitten" units should not be more than 10% of the total, but no less than one.
Next, we need a formula to calculate the chance of it working. Let's say the total chance is 15%, and it can be reduced if the army is larger or equal, or if the army is 1, 2, or 3 levels higher.
I think this is more appropriate.
Please also consider one more thing: notice that almost all troops of levels 6 and 7 are balanced, perhaps except for the humans; they have angels and paladins that are strong, but the angels are weaker than the shadow dragons, but the paladins are stronger than the matriarchs. The same goes for the elves. So, if the Krakens don't have a counter to the attack, we need to make the 7th-level troop weaker.
If you are interested in my ideas on this, I can try to objectively evaluate all types of troops in comparison with others.
P.S. You asked for help :)