Hail from Tolaria the ever changing 'Dane.

Masters Edition III

Halfdane

At the beginning of your upkeep, Halfdane's power and toughness become equal to the power and toughness of target creature other than Halfdane, until the end of your next upkeep.

At the beginning of your upkeep, change Halfdane's base power and toughness to the power and toughness of target creature other than Halfdane until the end of your next upkeep.

Legends

When Halfdane comes into play he is 3/3. During your upkeep, Halfdane acquires the current power and toughness of target creature other than Halfdane. If there are no legal targets, Halfdane becomes 3/3.