Jace's Sentinel

The whole card is a conditional wager on a planeswalker subtype. The body it ships with is a defensive crouch: a 1/3 that trades into nothing and pressures less, the kind of stat line printed to survive rather than threaten. The promise is the clause that fires only while you control a Jace, at which point the creature gains a point of power and becomes unblockable, turning a wall into a guaranteed two-damage clock. That structure makes it less a creature than a payoff card stapled to a creature, a design that wants to reward a deck already committed to a specific planeswalker rather than offer anything to a deck that runs it as a generic two-drop. The friction is obvious and intentional: control the right walker and the Merfolk is a quiet repeatable hit that no blocker can stop; control nothing and you have an under-statured body whose toughness is its only real virtue. This is one of a handful of creatures keyed to a named character's presence, where the text is a bet that the planeswalker is on the table often enough to matter. The reward never escalates: it is the same +1/+0 and the same evasion every turn, no scaling, no stacking. Everything hinges on a single binary condition, and without it the Merfolk does very little.