Does Fiora Legend's ability trigger when Shen is played from hand to defend a battlefield, or does Shen enter with the shield instantly so Fiora doesn't see him 'become' Mighty?

Ruling: Fiora Legend's ability does trigger when Shen is played to defend a battlefield. Shen does not enter with the shield instantly; he gains the defender designation during cleanup, which causes him to become Mighty and trigger Fiora.

Sequence:

• Shen resolves and enters play as a 3 Might unit
• Cleanup happens immediately after Shen resolves
• During cleanup steps 1 and 2, Shen does not yet have the defender designation
• In cleanup step 3, Shen becomes a defender and gains the shield
• Shen goes from 3 Might to 5 Might, becoming Mighty
• This triggers Fiora Legend's ability

Nuances:

• No players can play cards or activate abilities during the cleanup window, so you cannot respond with cards like Hextech Ray or Stupefy before Shen gains his shield
• You never get priority before Shen gets his shield