Nyxborn Eidolon

Bestow's pitch was solving the dead-card problem that plagues Aura-based aggression: a buff spell drawn against an empty board is wasted, and a creature drawn too late into a board stall trades down. A bestow card splits the difference by being both, with the mode chosen at cast time. Cast it cheaply for and you have a 2/1 to apply early pressure. Cast it as an Aura for its bestow cost and it enchants any creature (yours or an opponent's, though you would rarely give away the buff) for +2/+1, then survives that creature's removal by falling off as a 2/1 rather than dying alongside its host and handing the opponent a free two-for-one. That insurance against card disadvantage is the structural trick, and this is the most stripped-down statement of it: a plain body wearing a plain pump, the common-rarity floor of the cycle meant to fill a curve and demonstrate the keyword rather than warp a board. What keeps the rate in check is the gap between the modest stat swing and the steep bestow tax: five mana total for +2/+1 is a price you tolerate only because the keyword has handed you a creature you can fall back on, the entire bargain the mechanic offers. The one constraint worth remembering is that the Aura mode needs a legal target; with nothing on the battlefield to enchant, you simply cast the 2/1 and wait.