Accelerates Special trigger (cooldown count-1). If foe does not use magic or staff, calculates damage using foe's Res, and if unit’s HP > 1 and foe would reduce unit’s HP to 0, unit survives with 1 HP. (Once per combat. Does not stack.)
Hel Scythe does not calculate damage using the lower of foe's Def or Res, and therefore isn't affected by skills like Mystic Boost 3 and Splashy Bucket+.
Hel Scythe is triggered by the foe's attack and reduces the damage taken from that attack.
The unit with Hel Scythe only survives a single attack, so a follow-up attack will still be lethal.
If unit is exactly at 1 HP and is hit with an attack that deals 1 or more damage, Hel Scythe will not trigger.
If both Hel Scythe and Miracle can activate during combat, Hel Scythe has higher priority. The user's Special cooldown count is unaffected if Hel Scythe activates.
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Mystic Boost 3 and 
Splashy Bucket+.
Miracle can activate during combat, Hel Scythe has higher priority. The user's Special cooldown count is unaffected if Hel Scythe activates.
