Use this card to get rid of some of your opponent's key monsters, especially ones that usually do not help them in the Graveyard, such as "Light and Darkness Dragon".
Use this card while you have a face-up "Spell Economics" so you do not pay any Life Points.
After you activate this card, use "Serial Spell" while "Spell Economics" is face-up on the field, so you can use this card's effect twice without paying Life Points, and you can get rid of two of your opponent's key monsters.
If your opponent's hand and deck have no monsters of the declared Type and Attribute, you are permitted to briefly check your opponent's hand and deck to confirm that this is true. Therefore, by declaring an incompatible combination of Type and Attribute for which no monsters exist, such as FIRE and Sea Serpent, you can get a quick look at your opponent's hand and deck, enabling you to predict their strategy. This can also be used in combination with cards like "D.D. Designator", "Mind Crush" or "Prohibition".
This card can severely cripple any deck focused on a single monster card, such as "Blue Eyes"/"Red Eyes" Decks and "Dark Armed Dragon" Decks, or simply destroy an annoying monster, such as "Jinzo", making this card quite a worthy sidedecking card.
This is even more potent in a "Macro Cosmos" deck, as it will ensure that the opponent will not be able to recover their card once it's sent to the Graveyard.
Following up this card soon after with Soul Release can be even more of a deck breaker if your opponent doesn't have a means of recovering Banished cards.
This card can help get rid of your opponent's "Honest", be it in their hand or Deck.
In a "Dark World" deck, you can remove from play the sent monster with "Dark Smog", making it harder to recover and discarding a card.
This card can be very effective against an "Exodia" deck. By declaring DARK and Spellcaster, your opponent will likely be forced to send a piece of "Exodia" to his/her graveyard, as he/she will be very unlikely to have another of such monsters in his/her deck. All parts of "Exodia" are also limited, meaning that only one of each is allowed in a deck. Combine with "Soul Release", "Disappear", or other such cards, to practically guarantee victory, because your opponent will most likely not have a back-up plan. Because of this, "Abyssal Designator" is a very good card to keep in one's Side Deck.