Tactics for playing against Sylvan.

doesn't his aura of fear always work?
and his counterattack can be countered, for example, with pikemen.

For now, it can still be effective, it works ;) But in general, it depends on what you want to use the 4th level for... The Devil is mobile and can quickly take down a hero... But it's not a given that Death won't adapt her tactics, and then the Dragon will be able to, if he wants to!