Does Humility affect creatures that enter the battlefield after it resolves or only those already on the battlefield?

Humility has a static ability that generates a continuous effect: it makes all creatures lose all abilities and become 1/1. Because this is a static ability applying in the applicable zone (the battlefield), it applies to every creature that exists on the battlefield at any given moment — not just those present when Humility resolved.

Under CR 611.2, continuous effects generated by static abilities apply for as long as the permanent with that ability remains on the battlefield. The effect is not a 'snapshot' taken at resolution; it continuously recalculates which objects it applies to. Any creature entering the battlefield after Humility is already there immediately falls under its effect (CR 611.3b).

This matters for layer calculations (CR 613). Humility's effect applies in Layer 6 (ability-removing) and Layer 7b (P/T setting). If a creature enters with its own static abilities or printed power/toughness, Humility's continuous effect overrides those in the appropriate layers, leaving the creature as a 1/1 with no abilities.

Importantly, even abilities granted by other cards after Humility's effect is applied can be stripped, depending on timestamp and dependency rules (CR 613.7, 613.8). Humility is famously one of the most complex layer interactions in the game.

Example: Humility is on the battlefield. You cast a Llanowar Elves (normally 1/1 with mana ability). It enters the battlefield but immediately loses its tap-for-mana ability and remains a plain 1/1 creature with no abilities, because Humility's continuous effect applies to it the moment it exists on the battlefield.