How to create AoE indicators?

Greetings everyone, first time poster here, so sorry if this isn’t the correct place. I have been working on a 2D game where I have 2 dragons throwing attacks at each other, such as laser beams, fireballs, and the usual.

As you know, a cool game isn’t cool without big attacks that the boss can throw at you. Here is where the problem is, I can get the boss to attack just fine, but I am struggling to create a triangle/cone/ that indicates the range, the area, and the landing spot of the attack.

If anyone here plays MMORPGs or MOBAs, you know what I am talking about.

An example of what I want to do: the boss gets ready to fire 10 fireballs, warns the player by showing the area that he is going to fire at, then fires at that area.

Any help will be appreciate, thank you.

One of the ways would be using Decal Actor.

I did try that, but I could not get it to work, do you perhaps have any videos that would relate to my problem?

I did try that too, but couldn’t get it work, any elaborations?

use particles. good particle effect better than any decal.