If my opponent plays a spell to deal 3 damage to my 4 might unit, and then plays Stupefy (which reduces might by 1), does my unit die?

Ruling: Yes, the unit dies. When Stupefy resolves after the damage spell, the unit becomes 3 might with 3 damage marked on it, which equals 0 might with non-zero damage, causing it to die.

Sequence:

• Damage spell resolves, dealing 3 damage to the 4 might unit (unit is now 4 might with 3 damage marked)
• Stupefy resolves, reducing the unit's might by 1 (unit is now 3 might with 3 damage still marked)
• The unit dies because it has 3 might and 3 damage on it

Nuances:

• Damage stays marked on a unit unless combat finishes
• For effects that trigger on killing a unit (like Disintegrate's draw effect), the unit must die immediately when that specific effect resolves, not later in the chain
• If playing multiple spells, the order and timing of when they're played as reactions versus waiting for resolution matters for determining when the unit dies