Rampaging War-Constructs

{4}: Each player creates a 5/5 Colorless Elemental Construct creature token with "This creature must attack each turn if able.". Any player may activate this ability.
Elemental and Construct creatures you control gain +1/+1, Haste, Trample and "When this creature dies, add {c}{c} to your mana pool.".
Their last command was to destroy. Centuries later, they still obey.