Seirawan Hydra
An Elite Monster of multifarious might
Immune to non-lethal damage.
Melissa A. Benson

FAQs
Q: What does “non-lethal damage” mean?
The phrase "lethal damage" (lower case) is any amount of damage that would be enough to kill a minion. This is different from the keyword ability Lethal (capitalized). Therefore, “non-lethal damage” is any amount of damage that’s not enough to kill it. So, 1 Lethal (capitalized) damage or 6 normal damage will kill the Hydra.
Q: If two 3-power units defend against Seirawan Hydra’s attack, will they kill the Hydra?
No. Though damage is applied simultaneously, a unit looks at each source separately. So, in this case, neither of the sources are enough to kill it and thus the Hydra is immune to the damage.
FAQs
Q: What does “non-lethal damage” mean?
The phrase "lethal damage" (lower case) is any amount of damage that would be enough to kill a minion. This is different from the keyword ability Lethal (capitalized). Therefore, “non-lethal damage” is any amount of damage that’s not enough to kill it. So, 1 Lethal (capitalized) damage or 6 normal damage will kill the Hydra.
Q: If two 3-power units defend against Seirawan Hydra’s attack, will they kill the Hydra?
No. Though damage is applied simultaneously, a unit looks at each source separately. So, in this case, neither of the sources are enough to kill it and thus the Hydra is immune to the damage.