Darksteel Sentinel

Indestructible is a static ability.

A permanent with indestructible can’t be destroyed. Such permanents aren’t destroyed by lethal damage, and they ignore the state-based action that checks for lethal damage (see rule 704.5g).

Multiple instances of indestructible on the same permanent are redundant.

Vigilance is a static ability that modifies the rules for the declare attackers step.

Attacking doesn’t cause creatures with vigilance to tap. (See rule 508, “Declare Attackers Step.”)

Multiple instances of vigilance on the same creature are redundant.

Flash is a static ability that functions in any zone from which you could play the card it’s on. “Flash” means “You may play this card any time you could cast an instant.”

Multiple instances of flash on the same object are redundant.