'The Uninvited Guest'

Give a random enemy card 'Blue Balls' (-1 attack for each turn it doesn't attack, up to -3). 'I'm sure you'll find your way around... eventually.'

+1 attack if this card wasn't attacked last turn. 'You're learning to appreciate my presence.'

-1 cost to play if there are no other friendly cards on the field. 'Making myself at home, one habit at a time.'

Draw a card and gain +1 mana next turn. 'Don't worry, I'll always be here... in spirit.'