The Passive Voice in Iþún
In Iþún, the passive arose from a grammatical case, -aihjen, used when using magic to affect someone. Kind of like an accusative case, but only used when the verb has to do with magic. This grammatical case is still used in the active voice for verbs like kill, electrocute, shoot, basically verbs that are drastic and tied to death or an extreme change of state, but ultimately the case ended up being used with a conjugation of verbs (originally a form of the verb that was used to reverse spells or used in counter-curses) to form the passive. That grammatical case isn't necessary with those verbs in the active voice, you can use the partitive case, -ksa, as well, but the meaning would be more along the lines of "you tried to kill."
Example for the active voice:
Leð aþaihjen vallisa. - I killed him/her (I him/her-aihjen killed. Haven't got a proper name for this case other than what I've been calling the "morphative" case, open to better suggestions on what to call it)
Leð aþaiksa vallisa. - I tried/attempted to kill him/her (I him/her-partative killed)
There are two ways that make it obvious whether the voice is passive or active: if the verb has nothing to do with death or an extreme change of state, it's likely the voice is passive, but the biggest indicator will be the form of the verb. The way the verb works, is that it was used in the past in reversal spells, counter curses etc. so it simply reverses which noun in the sentence is the intended subject and patient.
Active:
Leð aþaihjen vallisa. - I killed him/her
Passive:
Leð aþaihjen vallisönnä - I was killed by him/her