Why put the hurt on someone yourself when somebody else has already done the work?
Remember Wound is an Astral and Blood spell of Moderate power that forces the victim to relive the worst injury they ever suffered. Depending on the target's luck, it can range from a stubbed toe to near-fatal wounds, as flesh remembers just how it was ripped open, bones relive being splintered, and organs unspool like before.
Blood must be spilled for Remember Wound to be cast; but it doesn't have to be the Mages.
Effect
Through the Astral, the mage captured the echo of an old injury, and through Blood, they cause the victim's body to erupt in the old wound. There's no limit to the extent of such an injury, though those who resist the spell can reduce or even negate the wound. Inherently magical creatures are more difficult to affect than mortals, but that's almost always the case. The mage can't pick which injury is inflicted on their target, nor does the spell take into account how the victim might have changed. A warrior whose worst injury was the loss of his arm suffers less as the stump is opened or the prosthetic falls off, for example.
Nor does the mage have any way of knowing what that injury is when casting the spell - a potentially fatal error if a Hydra's defining wound happens to be a multiple head decapitation.
The spell has a range of roughly visual sight, but more practically to a hundred feet or so. Some more poetic descriptions of the spell place the range as far as "still being able to see your foe in the eyes," though eye-contact isn't required, no matter how dramatically appropriate.
In the World
Remember Wound is most commonly cast on warrior types, as they're more likely to have been wounded in their careers. Others devise the spell especially because they know whatever rival they are facing once suffered some great and terrible injury. Due to the unpredictable nature of the spell and the cost of blood, it is usually saved for occasions that merit special attention. Others still manage to inflict some spectacularly lucky hit on an enemy in a battle, and just wishes to relieve their moment of glory once more.
Haha, the idea of someone casting it on a hydra and it being a huge mistake is hilarious. I like that you've included versions of the spell that lean more to the astral and the blood. That's really fascinating.
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I think an emerging concept of Ithekshem is that magic can always go wrong somehow
Creator of Araea, Megacorpolis, and many others.