Rotom (Ultra Prism)

Rotoms from Ultra Prism Series are very strong Pokemon since you don't need to attach Energy to use their Attacks. They have Ability called Rotom Motor which allows you to ignore Energy Cost for Attack if you have at least 9 Pokemon Tool Cards in your Discard Pile. All you have to do is discard 9 Pokemon Tools Card in order to use different types of Rotom with Roto Motor Ability.

In addition, having different types of Rotom is great to counter against Opponent's Pokemon. Because if your Pokemon Type is strong against your Opponent Pokemon, your Pokemon will incur double damage.

Fan Rotom is great Pokemon is a Starting Active Pokemon since it has no retreat cost and you can retreat anytime

Wash Rotom is Water Type and its Attack Wash Arrow does 50 Damage to 1 of your Opponent's Benched Pokemon. You can use this attack when your Opponent retreat its Pokemon due to Low HP.

Frost Rotom is also Water Type Pokemon and its Attack Frost Crush does 10 Damage + ( 20 Damage * Total Energy Attached to All your Opponent's Pokemon). This Attack is more suitable for late game as the games goes on your Opponent;s will attach more Energy Cards to his or her Pokemon and thus the Damage from Frost Crush will become massive.

This Electric Type Rotom is one of the highest damage Attacker among all Rotom. Its Attack Plasma Slice has damage of 120 but you can't attack next turn after you use this attack.

The Psychic Type Rotom has exactly same Attack as Electric Rotom and the only difference is their Type.

Mow Rotom is Grass Type and its Attack Special Mow has an effect of removing a Special Energy Card from your Opponent's Pokemon with 60 Damage.

Heat Rotom is Fire Type and its Attack Heat Blast has a Decent Damage of 80.

Discard Cards 

Battle Compressor allows you to discard 3 Card from your Deck to your Discard Pile. Since it is an Item Card, you can use as many Battle Compressor as you want during your Turn. You just need to use 3 Batter Compressor Cards to use all of Rotoms Attack without Energy Cost.

If you have Tool Cards in your Hand, you can use Professor Sycamore to discard your Hand and draw 7 Cards. Doing so not only discard your Tool Cards but also increase your chance of getting Rotom in your Hand.
 

If you have 2 Tool Cards in your Hand, you can use Sophocles not only to discard those 2 Cards but also you can draw 4 Cards.
 

Unown Ability Farewell Letter allows you to discard it if it is on Bench and draw card. You can use this Ability to discard 1 Tool Card by attaching Tool Card to Unown.

If you have 2 Tool Cards in your Hand, you can use Ultra Ball to discard those 2 Cards and put any Rotom in your Hand.

You can also use Field Blower to discard up to 2 Tool Cards because Field Blower allows you to discard 2 in any combination of Tool Cards or Stadium Cards. So, you can attach 2 Tool Cards from your Hand to your Pokemon and then use Field Blower to discard them