Halfdane

The upkeep trigger overwrites Halfdane's base power and toughness rather than layering a modifier on top, an unusual move in a period when most stat changes read "+X/+X until end of turn." The window is the more interesting part. The change persists until the end of your next upkeep, so the body you copy on turn four is the body you keep through your opponent's entire turn, right up until the next trigger arrives to retarget. That timing turns the card into a defensive mimic as much as an offensive one: the threat you point it at on your upkeep becomes the wall standing between you and that same threat on the swing back. The trigger is also mandatory, which makes targeting a liability as often as a tool. If the only legal target is small, Halfdane has to shrink to match it, dropping below its printed 3/3; and if the target dies after the ability resolves, Halfdane keeps the borrowed stat line until the end of your next upkeep rather than snapping back. The copy effect is deliberately narrow: it takes only the numbers, not the abilities, so there is no question of inheriting flying, trample, or a triggered ability from the target. It is a clean, early expression of the shapeshifter idea, written before the templating language existed to make broader copy effects safe to print, and it asks the rules manager to do real work for a body whose printed 3/3 is only ever a starting point.