For the first time, in a long time, WHERE IS IT?
Let me explain...
I set the Dawnguard quest to kick in at level 30 and forgot about it. I went about my business, collecting butterflies and mudcrab remains when the game freezes and up pops 'Windows Pure Virtual Function Call, R605 error'. This is the start of it.
I was level 29 and somehow Dawnguard things were rolling into action and you know when that error crops up that it's here to stay, and will keep returning, unless you sort it out. The only fix for that error I've found that actually works is to initiate and complete the St Jubius quests via console. But I haven't been to the Soul Cairn yet - heck I haven't even started Dawnguard yet! Am I really going to risk completing a Dawnguard side quest via console, without even starting Dawnguard proper. NO WAI!
So, only one thing to do - Dawnguard proper - With all the bells and whistles :) Initiate downloading a dozen Dawnguard mods, rebuilding Dyndolod, Patches etc, mmm, this is gonna be good.
And then I remember reading some tweak you can make to Dawnbreaker that turns the kill undead push explosion into a nuke, and is the weapon of choice to take to Dawnguard. DO WANT!
So now, I actually need the beacon, to get the sword, to go do Dawnguard, to get Bijin Serana, to visit Seapoint & Serenity, to check out Dawnguard overhaul, to see EoTW Dawnguard, to do all the Dawnguard things I've never done before, and check all the smart mods, just so I can type into console "setstage dlc1vqsaint 20/ setstage dlc1vqsaint 30/ setstage dlc1vqsaint 200"
I should have put "that'll be tree fiddy" at the end but MaxLemon would probably have spanked me for that, and frankly my arse has seen enough action for one day