Goblin Cartel cost {X} less to cast, where X is equal to the greatest mana value among permanents you control.

Whenever you attack with one or more creatures appraise an artifact you control (Choose an artifact you control, use its mana value to determine the following effect.) —

0-3: Create a 1/1 red goblin creature that is tapped and attacking.

4-6: Create two 1/1 red goblin creatures that are tapped and attacking.

7-9: Create four 1/1 red goblin creatures that are tapped and attacking.

10+: Create eight 1/1 red goblin creatures that are tapped and attacking.