TPKed the Party; Need Advice
Hi, I TPKed my party 20 minutes ago. For context, they had previously fought an Ancient Red Dragon severely under-leveled because they thought it was something else, but had managed to eek their way out through negotiation and by appealing to its over-inflated ego. The were forced to leave one PC behind as a captive & another was killed. They spent the last few sessions preparing and gathering allies from their home city and they even Planar Bound a Goristro for the battle (with help from the city; they have a kind of alliance and planned to share the hoard with the City). They came into the lair prepared to fight to the death knowing the Dragon's strength and how weak they were in comparison. They had 16 NPC's which I ran, the Goristro, & the 5 of them (level 6; low but I warned them several times & they knew the risks). The Dragon summoned 6 Wyverns, which they dealt with, but through a combination of bad rolls, being unable to successfully ground the Dragon, and a few breath weapons they couldn't hold up to it. I feel incredibly sad and guilty about this as we have been building and sticking with these characters for about a year now. They have relationships and everything and I know permanent loss is a part of D&D, but this almost feels like too much. I am stuck between leaving them all dead and moving on to not cheapen the loss or potentially having some alternative (advice welcome) to lessen the blow of the loss. I am conflicted because it feels like too large a blow to the story and everyone's enjoyment and I would really appreciate some advice. Thank you and goodnight!
Edit: Resolved!! Thank you everyone for your help & advice!