Counterspell Modifier is one of those Modifier that just makes magic units feel bad to use right away. The moment you see it, you already know melee and range units will be more common in the battle. Because of that, abilities that interact with melee and range damage become more important and you start building around them instead. This modifier is a battle of wits where it tests how good you are without the help of magic damage units.

Modifiers

Counterspell - All units receive the Magic Reflect ability at the start of the battle. Enemy units that attack with magic receive damage back.
Counterspell modifier gives Magic Reflect that returns a portion of the damage back to the magic attacker. This means you would most likely use less units with magic damage since there's a disadvantage when using those. The use of melee and range units gets more benefit and preparing for these are better.

Good Abilities to use in Counterspell Modifier

Shield - Reduced damage from Melee and Ranged attacks
Shield is very strong in Counterspell Modifier because most players avoid magic damage. This means they go for melee and range attacks which Shield can reduce by half. Having Shield on your front unit makes it very hard for enemy units to break through your defense. It gives you more time to deal damage while your tank just stays alive longer.

Thorns - When hit with a Melee attack, does damage back to the attacker
Thorns becomes very scary in this Modifier because melee units are everywhere. Every time they attack, they take damage back which slowly kills them. This is very strong especially if the enemy relies on full melee team. It creates a situation where attacking feels like a punishment for them which is really fun to watch.

Sneak - Targets the last Unit on the enemy Team instead of the first Unit
Units with Sneak, Opportunity or Charge is better since this gives your melee units more flexibility. You can use them with different positions even if they are melee units.

Amplify - Increases Magic Reflect, Return Fire, and Thorns damage to all enemy units by 1
Amplify is a bit situational in Counterspell Modifier but it can still work. It increases the Magic Reflect damage which punishes enemy units even more if they still use magic. Some players ignore the risk and still go magic so this ability can surprise them. It is not always useful but when it works, it feels really strong and satisfying.

Void - Reduced damage from Magic attacks
Void is the only reason you might still consider using magic units in this Modifier. Since the reflected damage is still magic damage, Void can reduce it. This makes your units survive longer compared to normal magic units. It is still risky to use magic but with Void, you at least have some protection and can make it work in some situations.

Battle Summary

This has been day 5 of me using Elowen Sylphie and I finally found someone using the same archon and strategy. I like that they also know the secret of using Resurgence on a Scavenger unit like Endless Ape. This was a very interesting battle since I really thought I would've win and that I had the advantage. The difference of positioning with Lioceros made a huge difference. My units getting hurt by the Thorns and my Lioceros getting destroyed by Thorns and 4 Resurgence in total hurt my team a lot. At the same time, I never expected to see a similar lineup so I never expected someone not using any melee Sneak unit or having a similar lineup so I guess that's fair. If the enemy was using a different lineup or strategy, I would've won this battle easy.

To see the full battle, you can click this link:
https://splinterlands.com/battle/sl_65c7e7df67b8c374ea526562dda8f85a

Counterspell Modifier is simple but very punishing and forces players to adjust their strategy. It makes magic units risky and pushes players to use melee and range units more. In my experience, it creates very fun battles because you need to think more about your choices. If you adapt well, you can easily win but if not, you might end up killing your own units.