Fun with old artifacts

At the beginning of your upkeep, put a doom counter on this artifact. At the beginning of your draw step, this artifact deals damage equal to the number of doom counters on it to each player. : Remove a doom counter from this artifact. Any player may activate this ability but only during any upkeep step.

At the beginning of your end step, target opponent gains control of this artifact and puts a charge counter on it. At the beginning of your upkeep, this artifact deals damage to you equal to the number of charge counters on it. : Put a charge counter on this artifact or remove one from it.

During your turn, prevent all damage that would be dealt to you.