Mercury square Lilith (orb 0.6°) creates concrete friction between the two planets. The orb is extremely tight; this aspect is one of the chart's strongest signals.
Here, Mercury in Leo in House 12 brings intellect, language, thought, and technique into House 12 (retreat, contemplation, long time, and possible confinement), with Leo style (presence, pride, creation, and the wish to be seen); Lilith in Taurus in House 9 brings pure ideal, absolute demand, fascination, and refusal of compromise into House 9 (vision, belief, study, and wider horizons), with Taurus style (nature, good food, physical sensuality, roots, resources, and perseverance).
Concrete friction: this aspect creates tension between thought, speech, obsession, purity demand, and refusal to let go. Visible angle: Mercury near the Rising sign (orb 3.8°) touches an angle; this aspect is easier to notice through first impression, body language, reflexes, and entry style. House 12 (retreat, contemplation, long time, and possible confinement) is in friction with House 9 (vision, belief, study, and wider horizons); this can create blockage, inhibition, overreaction, or repeated conflict between the two fields.