二级

二 = 一 : Mnemonic symbol: a capacitor, because the two strokes remind me of the symbol in electrical drawings. Albert Einstein (Ø) is experimenting with a capacitor (二) in the space station's bathroom (Ø4). He finds that it's uncomfortable to discharge a capacitor using two flutes (一).

级 = 及 + 纟 : Joan of Arc (ji) closely investigates her newly arrived troops just inside the space station's entrance (Ø2). She ranks (级) them according to their level (级): First there is a silk worm (纟) which can at least shapeshift. On the next level, there is Yuwen Huaji (及), who has no comparable super power.