Just because Leviathans can negate regular Angels' powers, doesn't mean they can do that to Archangels.
The creations of the alphas would not automatically alert somebody to leviathan in purgatory, purgatory is locked and is a prison that later become an afterlife, since it takes various rituals to even open it, is it no safe to assume that Eve was not always there? he did not let them in, he took in the souls of purgatory and the leviathan hitched a ride, when he tried to get them out, the proved to be too strong, even when he had the power of millions of souls it was the leviathan that were taking over. Who said anything about needing to kill them for the win? the only angel that didn't die as a result of his vessel being harmed was Michael, but he also was in charge of heaven and all it's powers and for all we know God brought him back after the same way he has done for Cas twice. The Leviathans are a race of ancient monsters that were created after the Archangels, making them the second living species in existence.
Eve can turn their powers on and off as she pleases, because as she said she is older and knows how to do such things, it's not far fetched to believe that she simply hid that information from angels, as they can be tricked and bloked from seeing things if you have the right mojo. But I still really like them. Cas made this comment but was not aware how old or powerful Eve was, nor did he know how to get in, or that another native of purgatory had been on earth for years without anybody knowing, IMO the angels have very high opinions of themselves and think they know everything out of sheer arrogance. And as stated it wouldn't matter if they invesitgated before or not if Eve has the power to hinder them. [Source]. Sometime after he bound the Darkness, God locked away the Leviathans in … It brings me back to Deaths comments, the universe is vast and full of planets and earth is barely out of it's diapers this would suggest that there are other places of interest if the Earth is lost. Leviathan have the ability to take over vessels that have angels in them and kill the angel in the process. They would be little work for an arch angel. No Archangel has ever been defeated by ingredients I can find in my bathroom. But when they took over cas, there were hundreds, or thousands, of leviathans inside of Cas and leviathans only able to tear apart Cas becasue Cas voluntarily absorbed them in first place. We've seen the Leviathans are more powerful than Angels and can kill them quite easily. Other than warping up house cleaner and pissing them off, what other tatic can archangles use? The power gap between archangels was wide, Gabriel and Raphael were not on the same level as their brothers. (As I said this is just speculation on my part). The arch angels were raised by God and had a "father/son" relationship with him so to speak. Only the archangels have even seen God, but for some reason Cas with the power of those souls thinks he is God level, he is fully aware of the power of the archangels, if he thought he was God it was because he was more powerful than archangels, since they are the only things he can compare his power to.
@strider good points, but if you can't kill them you can't win.
So, in conclusion, leviathan can devour archangels, albeit it might burn going down.
They would have no trouble stopping it from doing anything. https://supernaturalfanon.fandom.com/wiki/Leviathans_(Between_Angels_and_Demons)?oldid=58543. No, both Lucifer and Gabriel did not think they can take out their older sibling easily. God himself created an enitre dimension just to get rid of them. Supernatural Fanon Wiki is a FANDOM TV Community. They obviously couldn't handle an Archangel, though. So, in conclusion, leviathan can devour archangels, albeit it might burn going down. Raph is the 3rd which means if Cas with a few thousand souls can match him Cas at the point is at least Lucifer level, so taking millions of them makes him higher. Personal information He took them in but neither him nor the ritual to release the souls of purgatory could send them back, when they decided they didn't want to leave, they take over bodies with that black goo, just seems to me they could enter his vessel whether he wanted them to or not, same way they didn't leave it even though that is what Cas wanted. Now if we go by that if a human can subdue and cut the head off a Leviathan an Angel should definitely be able to now throw in the fact that Arc-angels are reality warpers who create stuff out of nothing all one would have to do is imagine a swimming pool full of Borax tie the headless body to a chair and throw it in. He could if He really wanted to, but he just locked them up becasue Leviathans are still his creations, or children in his perspectives. Of course God can kill Leviathan because he is God, but God is infallible, so if he makes something unkillable then even he can't kill them, because if he does he becomes fallible and no longer God.
It's also a fact in SN God apparently left Heaven and the angels to do their own thing after he was done creating and punishing rouge angels, for all they knew the monsters were a new creation of his, magic is very real in SN and some humans have become monster even through science so that is how monsters can be around and not raise an issue or alert anybody to what is in purgatory other than their souls. Sure, it wont kill them, but will most definitely prevent them from killing anyone for the time being. That's a part of the reason why the muated Cas is not more powerful than Archangels.
Even angels are powerless against the Leviathans.
These beasts were among God's earliest creations, predating angels and humans. Angels do not know about Leviathan at all and humans stumbled upon the weakness because one was cleaning the house, leviathan on the other hand know everything about angels thanks to Cas @buttersdaman please provide proof for that, because going by feats Raph and Gab have more and greater feats than Mich and Luci. If Lucifer hates Demons and Pagan's so much I doubt he would let out something from Purgatory he would despise even more, not to mention might even rival him on power. @LordOfAllHumans: Oh i'm in agreement that Cas had no idea about Eve or the Leviathan's. Binding is easier than un-binding, just likes it easier to make a knot, untying it can be a bitch. However, in both casees, God did not kill his rouge children; he just created dimensions for each of them in order to contain them inside safely.
So we can't really say that the older and higher ranked Arc-Angels know nothing about them because we haven't seen them in the current series.
As far as we know Cas is dead and there is nothing to suggest that they only destroyed his vessel and not him as the killing of an angel has always been done by attacking said angel while in a vessel. I doubt archangels can do something that apparently not even God and Death can do.
Remember when Castiel was speaking to Dean about the Apocalypse? Another reason i don't think they would be interested in inviestigating them is because until the coming of the Apocalyspe they have shown no interest whatsoever in Earth, even in the future where Sam said yes and Dean didn't, the Angels simply left Earth alone because it was no longer important to them, this was a future seemingly created by the angels and in this future they show Dean that Earth is not as important to them as it is to us so they just bailed on it. Every Angel in the show was certain that Michael would stomp. Archangels are angels, so unless it is stated otherwise on the show, Leviahans can kill archangels (being angels, which Leviathan can kill). The leviathans are a joke. - …
This is my theory (of course I can't back it up completely but i'll give it a go). Take your favorite fandoms with you and never miss a beat. Holyserpent as usual says and knows nothing.
most beings in the show with the expection of the ones that were in purgatory and Death thought there were only souls of humans that became monsters down there.
Death's perception of them doesn't prove anythin'.
From what i've seen the only thing so strong about Leviathan's is their durability due to the lack of knowledge on how to kill them. So assuming he did know about them would he really try and free something that God himself said where poisonous and untrustworthy?
He's basically SN's whipping dog he seems to lose every fight and not know much about whats going on (I was actually happy when he absorbed the souls I was thinking "Yay Cas is actually gonna beat someone for once!").
they were in the vessel of an angel that was more powerful than an archangel and they took over when he has the power of "God" and then killed him later.
Cas was afraid to let Michael out of the cage. Leviathans
@Strider like i said before good points, but the leviathan as stated by Death are too clever for that, it's why God locked them up, he had no problems with having one of his children beat the hell out of another to prove a point, if he made archangels with the ability to kill leviathan there would be no reason in locking them away, he could just as easily send his four sons to take them on then and there. doesn't matter how much reality you can warp if what you are trying to kill can't die as deemed by the most powerful reality warper, God. Castiels sole purpose was to get enough souls to become more powerful than an archangel, SN never said this archangel is more powerful than this one, all it ever said is that they are absolute and groups them all together as the same kind of angels, fans made the assumption that one must be more powerful than the next simply because one is Lucifer and most people erroneously believe that Lucifer is as close to God level as you can get with the expection of Michael when in fact there a other angels that closer to God then those two.