Trail of evidence

Whenever a creature enters, you may add an amount of equal to the number of creatures you control that share a creature type with it.

: Put a charge counter on this artifact. Remove a charge counter from this artifact: Add one mana of any color.

Buyback (You may pay an additional as you cast this spell. If you do, put this card into your hand as it resolves.) Choose a counter on target permanent or suspended card. Remove that counter from that permanent or card or put another of those counters on it.

As this creature enters, choose a creature type. This creature is the chosen type in addition to its other types. Other creatures you control of the chosen type get +1/+1.