Legendary Card suggestion.

Legendary Card The Council 1,000 no attack Ability- Contract: create a contract on a targeted tower that Cannot be removed. 1 time use. Coin max 100 Coin: when reaching max coins the council will grant the tower holding the contract a Stat boost, and reset the coin count. Stat boost: 10% damage/attack speed , 20% crit damage 5% crit chance every 5th boost gain +1 multi crit on 10th boost Grant 5% on attack to generate a second attack mimicking the damage done. (all stats appear on the contract) The councils Contract: -75% gold each kill generates 1 coin

Like the idea! Stat boost seems a bit strong to me!

of course, needs to be refined for balancing.