It turns out that Elden Ring players can kill Shadow of the Erdtree's final boss with the power of friendship and a strange bug
An Elden Ring player who goes by Los Ch. ロス stumbled upon a ridiculous bug for Promised Consort Radahn, the final boss of Elden Ring: Shadow of the Erdtree. After further investigation, it looks like this strat is replicable.
If you summon two phantoms in co-op for the Leda fight and kill her without anyone else dying, Promised Consort Radahn will drop dead before you even reach his bonfire. "Batshit CRAZY Promised Consort Radahn skip," the player says alongside a short video. "I've replicated this bug and it seems like it's consistent."
The video that's linked shows Los Ch. ロス and other co-op summons jumping Leda (it didn't seem like she stood a chance, honestly). After spawning in Enir-Ilim, the player makes his way up to Promised Consort Radahn, only for the God to be slain halfway up the steps. As Los Ch. ロス reached the entrance to the boss fight, there was no fog door to be seen, and all that was left in the boss room was a lost grace and a few blood stains.
It's certainly a strange bug to encounter, especially so late into the DLC's release, especially with all the streamer challenges and one-hit runs against Radahn. Although a couple of commenters on the YouTube video suggest that this bug has been encountered by more players than just Los Ch. ロス. "Had something similar," one player says. "Entered as a phantom, but Radahn never jumped down and was invisible." Others explain that they encountered similar glitches either on PC or during the second phase of the fight, with one player even linking a video of the glitch happening to them.
After Elden Ring YouTuber Ziostorm posted about this bug, a couple of players theorised that it could be caused by the Seamless Co-Op mod getting messed up. However, Ziostorm does point out that the initial video was taken on Xbox. "I can confirm I've done it twice now, and both times it'll say "God Slain" give me my runes and boot me off," another player says. "I've messaged the host after asking if the boss is still there, and they said yes and summoned me back for it." So, the fix for this could just be as simple as refreshing your game or resting at a bonfire.
Co-op play is a fairly important feature in Elden Ring, even if you prefer to go about things alone. With this feature, you can play with friends or even summon local folk heroes like Let Me Solo Her (now known as Let Me Solo Him for the DLC) to help fight bosses that may just be slightly too difficult for you to take on alone.
This feature is so popular that there's even a mod that'll let you play through the entire game with seamless co-op. Usually, you can only summon co-op phantoms for a single fight, and they'll disappear once they die. While this may not be entirely in keeping with the rules that FromSoftware has laid out, it turns out that the devs aren't in total opposition to the mod and may even "consider ideas like that with our future games."