They Honestly Won't Ever See It Coming

Whenever Karn blocks or becomes blocked, it gets -4/+4 until end of turn. : Target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value until end of turn.

Equipped creature has ": Add one mana of any color." Equip

Reach (This creature can block creatures with flying.) Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Equipped creature has ", : This creature deals 1 damage to any target" and "Whenever a creature dies, untap this creature." Whenever a Shaman creature enters, you may attach this Equipment to it. Equip

If you tap a permanent for mana, it produces twice as much of that mana instead.