Syndicate seems to be the faction that have been sort of lagging behind on utilizing the power of Renfri. Or at least not much meta/competitive decks are having some presence to my knowledge and experience.

Here's one. It's a fantastic, genius idea that totally didn't get inspired by past (2-3+ months) popular Off the Book decks dominating the game. Nope it was all me and my lazy self :D. Seriously though, if you played the game last few months, you quite likely have played/faced or at least seen versions of it.

It uses the power of (still op op) King of Beggars acting as a an extra (invisible) card in hand every time you end up using a tribute. It refunds it back as if it costed nothing and after counter is gone - boom you have a spender and thinned deck. That coupled with a bunch of (no place to be in this archetype) firesworn cards creating big tempo due their (busted state) lets you get ahead rather easy! Cheap spending tools like Fire Disciple and Inquisitor (I play for 10/4), together with the (now changed into non-interactivity to make a poison deck viable) Gellert you'll have a decent amount of points to close r1 successfully.

Of course you need some tribute cards to get advantage of King of Beggars. In my case I've put (and the previous meta decks did so as well). Jacques, Moreelse, Salamandra Mage, Shady Vendor and Renegade Mages. Last one is a card open for replacement as her 1 tribute is negated due your Leader ability (makes tributes cost 1 less). Is it bad, no, but it doesn't trigger counter on the Beggar which in some cases you might actually want so he gets out. Hey it's 7/4, 3 of which are damage and I am complaining - these day and age of Gwent... Fence is alternative at the 4p slot.

The other cards try to symbiote well enough with firesworn or be open to versatility and what might suit the needs. Cyrus is great to bring back a Disciple or Inquisitor from graveyard. Another addition that can boost his presence and help Beggar with tributes is Cleric of the Flaming Rose. For that one you'd need 2 5p spots and a bit more deck tinkering.

I've put one Tax collector (sometime with no Salamandra Mage on board) you'd need a bit of coin. Pellar (you better have one or 2 :P). Failed Experiment - a rather recent change - because having a unit that can poison others with Gellert offers good opportunity to get rid of big unit. Something this deck can struggle with. With that addition you can consider Moreelse and poison as your answers for big threats. Shady Vendors played in front can also give you poison - so there you go - decent versatility. On that note I did consider having Runemage opening/guaranteeing the create possibilities even further. For that you'd probably take out Cyrus and use the extra 2 p for the aforementioned Cleric of the Flaming Rose. Voila - another take (with Walter Veritas, why not :)).

Dorregaray at 6p is a card you can substitute with what you need. As Locks seems to be 90% of time always purified. You might add banish with Lemmens or consider upgrading/downgrading another card. I wasn't fully sold on the lock.

Kinckers and Roach to help thinning. Triss Butterflies (power creep me Matta) to guarantee whatever card you want. It also helps fixing a brick.

The last few cards are the Renfri package (and what package she has). Renfri's Gang and the lady herself. Obviously the first is a fat thinning 12 split into 2 bodies. Renfri itself is currently the bane of the game due to how powerful she plays for. Great and interestingly designed card - the reason you play only units is because of her. Will see if she will be nerfed into non-existence or some of her presence will remain. Well duh, basically every damn op deck from the past/current day, that was never addressed by CDPR did a take with her, just like I do so right now, I am amazing!!!.

As to her options she has 9 curses and 9 blessings, you preferable play ones you need at the moment (don't look at me removal - khuh, khuh).

With this version though, more often than not you use her as a finisher or 2 round win card. The reason why not many folks attempt to play her with SY is because the good leaders (oh look, good game design) usually synergize well with the cards you play. Due to Renfri replacing your leader with a new one you lose a lot of that important trait on left cards. That's why Lined Pockets, Jackpot, Hidden Cache or even Off the Books can suffer and are not "suitable" with her. In actuality the best ones are Blood Money, Congregate and Pirate's Cove. Alas they are not very good in general, but I admit I've seen firesworn deck with her :D. Who knows people might be sleeping on of those leaders with her, huh :).

To returned to Renfri and Off the Books. Yes you do try to keep her as card played later. You start off if you can with Gellart or Disciple. They produce 2 points a turn for 1 coin each. Add an Inquisitor, a thin card or 2 pop/are played and suddenly you have quite the tempo and presence on board. Consider Experiment as poison removal and don't be afraid to jam tributes or using leader. With a Sala Mage on board you might even need more spenders (I had one Jackal before). Mage is still great card and in typical fashion even a slight nerf seems to leave an op card neglected - in this case we had new cards/meta shift as well to account for.

The above stuff often will be enough to get you r1 win. You decide if you want to bleed r2 (usually I'd say yes, if you can) or go for r3. Try to get out at least King of Beggars before using Renfri or you have to re-calculate a lot of the tribute interactions.

I'd say deck is yet achieve a the most optimal state, a better fine-tune can definitely improve it or have different take (as I did with some suggestions). I had a more dumber version with more thinners - the 2 5p SY cards - yes it was totally brick house, but was more simple to play - just jam cards, don't care, what else do you need.

Try to have fun!