How to make objects transparent at render.

In my game I have different types of characters and certain types can see different characters.

Eg Human - can see only other Humans

 Spirits - can see Other Spirits and Humans.

How will I accomplish this?

And I want to make it possible for the Human to gain the ability to see Spirits over time, so i thought about adding a float value that sets transparency so if the float is at 5.0/10.0 the person can see the object but not the details.

Is it possible to add a material on it but will only change on one instance of the game for Multiplayer purpose.
I want certain characters to be able to see certain object/characters

To do this you simply have to change the visibility of the enemies using code. There is a node called “set hidden in game” and if you feed this node a true value it will be invisible.

Every time you switch you have to make sure you update these changes so i would make a check inside the enemy blueprint that sets these values depending on what the player is.

For the transparency over time mechanic you must use a translucent material where you update the opacity as the game progresses. To do this you should make a material parameter collection with a scalar value called “opacity”. Set this value to 0.0 in order to hide the enemy and 1.0 to be fully visible. Then simply connect the material parameter node to your opacity pin in your material.

HTH

Your idea would work in a single player situation but not in multiplayer situation.
I need it for a multiplayer situation