Oakenform

The pure stat-pump Aura, distilled to its arithmetic: three mana for six points of stats split evenly across power and toughness, with no keyword, no upside, no rider. This is the baseline against which every Aura with text gets priced. The trouble is the price was always too high, because the Aura tax (two-for-one risk built into the card type) was identified and punished long before this design existed. Spend the mana, commit the card, and a single removal spell takes both pieces while you've spent a turn doing nothing to the board. That math is exactly why the green creature-buff Auras that actually saw play came packing insurance: trample to push the bonus past blockers, or hexproof to make the removal answer cost a card it can't profitably spend. Stripped of any such clause, this is the cleanest illustration of the problem the genre spent years solving. It exists less as a card to play than as the control variable in a long-running design experiment: hold the +3/+3 and the three-mana cost constant, then add a keyword and watch the card go from unplayable to format-relevant. The pump is honest; the vulnerability is the whole reason later Auras paid for trample.