If any basic Energy card attached to Flygon is the same type as any of your Pokémon, the Retreat Cost for those Pokémon is 0.

Sand Wall

40

Discard a Stadium card your opponent has in play. If you do, prevent all effects of an attack, including damage, done to Flygon during your opponent's next turn.

Power Swing

60+

Does 60 damage plus 10 more damage for each Evolved Pokémon on your Bench.