Cryogen Relic

The two card draws are the load-bearing part, and the sacrifice ability is the excuse to collect the second one. An artifact that replaces itself on entry is a familiar trade: you pay two mana for a cantrip that happens to sit on the battlefield for a while. What this design adds is the leaves-trigger, which turns the sacrifice cost into a draw rather than a tax. Cracking it for the stun counter is not a loss of card advantage; it is a second cantrip stapled to a soft removal effect. The stun counter itself is the newer half of the equation: it does not kill anything, it only keeps a tapped creature from untapping once, which pairs the ability tightly with whatever already forced the target down (an attack, a tap effect, an activation). That restriction is what keeps the two-for-one honest, since you cannot point it at a fresh untapped threat. Read as a whole, it is a value permanent that pretends to be interaction: the artifact wants to enter, sit, and eventually be sacrificed, banking two cards across its life while occasionally locking a blocker or attacker out of a turn. The stun mechanic doing the tempo work here is a clean fit for blue, which has long preferred to delay a creature rather than answer it outright.