Aura tower

[Rekun1love]

How to make an aura tower which will make a damage inside its range to multiple enemies?
When an enemy or multiple of it come in the range, tower starts to make a damage each second to every single target.
And how to make a slowing aura which will slow enemies in its range when they enter in it.
When an enemy or multiple of it come in the range, it starts to slow them down smoothly to the definite number of their speed.
And when the enemies came out from this range, they start to return their movement speed also smoothly to the default speed amount. Ot dyshi