Maildramon (BT27-062) - Ignition of X

[When Attacking] [Once Per Turn] You may play or use 1 card with [Knightmon] in its text from your hand with the cost reduced by 2.

[All Turns] [Once Per Turn] When this Digimon would leave the battle area, by deleting 1 of your other Digimon with [Knightmon] in its text, it doesn't leave.