If Jax (who has Weapon Master) is already in play and then Svell attaches to him, does Jax get a second Weapon Master trigger?

Ruling: No, Jax does not get a second use of Weapon Master. Weapon Master is an ETB (enters the battlefield) trigger that occurs when a character is played.

Sequence:

• Jax is played and his Weapon Master trigger activates
• Svell attaches to Jax later, copying Weapon Master
• The copied Weapon Master does nothing because Jax has already been played

Nuances:

• Svell does copy the Weapon Master ability, but gaining the ability after the character has already entered play does not grant another trigger