Use this card when "Spirit Barrier" is on your side of the field. This way you won't lose Life Points from the opponent's direct attack.
This card can be useful for avoiding your opponent's "Honest".
Use this card to protect a monster brought out with "Relay Soul," as you won't take battle damage while it is in play and you reduce the risk of losing the game via its destruction.
Use this card to protect an "Injection Fairy Lily" if they attack it with a monster which prevents damage from occurring normally, such as "Exploder Dragon" or anything protected with "Waboku" (which would normally render her ATK "pumping" effect moot). Plus, on your next turn you can attack directly with "Lily" with a pumped-up 3400 ATK.
This card is an awesome counter for when your opponent tries to Bounce away a high ATK monster with "Neo-Spacian Grand Mole." Not only will your monster be saved, but you will take a negligible 900 damage while your opponent will take two monstrous attacks, which can rapidly deplete their momentum.
"Etoile Cyber" can function with this card – as she did in the anime – give that her effect boosts her ATK when she declares a Direct attack (note that this will probably not be too useful, as you will only inflict a total of 2900 damage).