Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Magewright's Stone

{1}, {T}: Untap target creature that has an activated ability with {T} in its cost.

{2}, {T}: You may tap or untap target creature.

You may activate abilities of creatures you control as though those creatures had haste.
{1}, {T}: Untap target creature.

Equipped creature has "{3}, {Q}: This creature gets +2/+2 until end of turn." ({Q} is the untap symbol.)
Equip {0}

{1}: Untap Staff of Domination.
{2}, {T}: You gain 1 life.
{3}, {T}: Untap target creature.
{4}, {T}: Tap target creature.
{5}, {T}: Draw a card.

{T}: Target permanent becomes an artifact in addition to its other types until end of turn.

Whenever a player casts a red spell, you may pay {3}. If you do, untap target permanent.