As we all know, it can take a year or more to collect enough ascension materials for a 5* hero… So Who gets the Royal Tabbards & why?
Here are my eligible Dark Heroes:
Freya, Alfrike, Clarissa, Quintus, Domitia, Victor, Obakan.
I already have Ursena & Kage into talent grid.
Thanks in advance for your input.
I would ascend freya, a fast pseudo healer
Alfrike or Freya.
Alfrike - there are enough rush events that she just crushes that seems worth it
Freya - fast pseudo healer who’ll also work wonders on map stages
I like Alfike or Freya most but don’t count out Clarissa, Kage can chop them down and then she finishes them with poison, speed kills
My vote goes to Alfrike, though she’s ideal for players with a deep bench already. But for players with shallow bench, Alfrike wont be able to enjoy her that much. I don’t have her though but I am on the stage where I can afford leveling a lot of prized or niche heroes.
I’m gonna say Clarissa given what you have maxed currently. Ursena takes a while to fire unless you have a lv 23 mana troop, and she doesn’t exactly have the tankiest build, so Clarissa’s elemental link really helps to keep your purple stack alive.
As much as I enjoy using Alfrike on offense, because of how slow she is, I almost wanna say you need to pair her with Clarissa to protect her against specials and buy more time for her to fire.
Freya is a bit more niche and doesn’t really synergize too well with what you already have. Of all the choices you listed, my vote goes to Clarissa since she will have the best synergy with your current heroes, and will become even more useful as you ascend more purple 5* and start running 4-1 or even mono.
Just a little note, if OP has Ursena+20, it only need mana level 11.
In this case I would priority 2nd and 3rd mana troop level 11.
Alfrike is monster on defense and I hate facing her. I do not have her.
And popular advice usually focus on offense heroes first. Well I know Alfrike is also good on offense though.
But Clarissa element link seems good choice for offense purple stack synergy like @rho said.
My Clarissa is still at 3.70, so I just seeing on paper theory.
I’d go with Alfrike but you couldn’t go wrong with Clarissa either. However, those are the only two you should be considering. Freya’s minion summons is good but there are plenty of heroes that could exploit/counter that.
Alfrike.
Then Freya.
Then save tabbards for upcoming heros. Gl. 
I’m actually not a huge fan of Alfrike on defense unless you have her at +20 with at least a lv 23 troop. At very slow she isn’t really ideal anywhere except tank*, but even then she’ll still have to eat I think 15+ tiles before she fires. That just gives the attacker way too much time to play the board.
*unless you have a suitable yellow tank, then she makes for a very good purple flank. But here’s the problem: the two best yellow tanks - Guin and Onatel, are both wizards!! I’m almost certain this isn’t a coincidence, because a Guin/Onatel tank with an Alfrike flank is kinda broken. I guess you could always try to tank Sif but she doesn’t have tanky stats, and her riposte can be easily dispelled by Domitia/Seshat/Panther.
+1 here 
Thanks so much for all of the input! Muchly appreciated!
I weighed all advice & went with Clarissa. Thnx!
I agree with @Deuce, Alfrike would get my tabards. She hits hard and with the mindless attack, is great at clearing a board. Team her with a fast mana troop, and the opponents barely stand a chance.