Cloak of Shadow:
Cast as required . You ma y evade any creature or character u ntil the start of your next turn.

Can I cast Cloak of shadow at the start of my turn, even if it's not required (because there aren't creature to evade)?

Can I treat "As required" like "At any possible time"?

Cloak of Shadow:

Cast as required . You ma y evade any creature or character u ntil the start of your next turn.

Can I cast Cloak of shadow at the start of my turn, even if it's not required (because there aren't creature to evade)?

Can I treat "As required" like "At any possible time"?

This is very ambiguous wording, as the interpretation of the word "required" can be very subjective. But since the spell simply grants an optional condition ("You MAY evade...") it's really hard to imagine a place where it could be either required or not required. Just because you have cast it it doesn't mean that you have to evade anything. And since it merely gives you the option of evading, you don't even need to encounter any creatures or characters to fulfill the conditions of the spell. Perhaps you are "required" to cast it just for the sake of making room for more spells.

So yes, you may cast this spell at any possible time, whether it is your turn or not, whether you are evading anything or not.

Same thing with Invisibilty:

"Cast as required . Y ou may evade any creature or character until the end of this turn ."

Too much complex for beginners and precise players. I think "At any time" could be a better choice. I just hate "As required", I don't understand why this exists.
Every spell in the category "as required" can be explained wording differently "at any time" instead.