According to Kalista's lore, she went to the pre-cursed shadow isles known as " the Blessed Isles" but Hecarim killed her so he could give the healing spell she hid to the king in order to not only revive the queen, but to also become the king's favorite knight. So was it Hecarim killing kalista that cursed the Isles or was it him revealing the spell?
It was a mix between the spell of necromancy created by the Ruined King, a curse that the Ruined king did after the failed ressurection of the queen, the skull of Mordekaiser and other magical items that were in the Shadow Isles
Read the lore of Hecarim, Thresh, Yorick, Maokai and Mordekaiser to learn more
Blessed Water of the Isles was defiled by the corpse of Ruined King's wife. Blessed Water has unbelivable healing powers but It was never have meant to ressurect. That's what I remember from Yorick bio.
There must be necromancy too somewhere of this case.
Maokai's updated lore is a good reference for what happened to the isles
maybe one day riot will write more about shadow isles that doesn't just go on about the harrowing with lucian and mf
Basically the king broke the 1 rule of the blessed isle..which started the curse that turn it into the shadow isles.
