I think the Ring of Pain pack in combination with the Blacksmith's Pack is a very good combo.

The evolve mechanic basically gurantees that you always have something to upgrade and you can shortcircuit the requirements by just using the normal Blacksmith upgrades.

Go with the Flow and Warlock is kind of nuts. Putting lots of Imps in your deck and then constantly flowing through the deck I've built up some pretty big imps. I also always take Transmutation if given a chance as it can make bad luck or bad picks into something useful.

Flow and Alignment are great, as are Eldritch and Distortion; the latter two also combo *very* well with the Claw pack and the Silent packs, which feature lots of ethereal/exhaust stuff.

Mad Science has a LOT of these, the standout(ignoring infinites and game logic exploits) for example:
Attach+Dominate(quanta, can now spam stun effect)
Cheapen+Claw for one is also pretty good
Attach+double poison card(toxicity, you can now cause poison to double more than once)

Then there is blacksmith/ring of pain+Claw, specifically Searing claw, as both of these have ways to upgrade a lot of times, thus buffing searing claw a lot

Pixie and Prismatic pair well with each other and any pack that has base game cards, since those count as different colors. Generating Shivs, Ghost Claws, Cannonballs, Fading Embers, etc also count as Colorless cards.

Witch pack is great with any other kind of orb, since the actual Witch orbs are pretty weak but Manifesting them to gain slots and using the Inscribed keyword pops off with better orbs. Inscribing Frost orbs is super strong, as is the Menagerie pack.

Rip is great with Statuses, all the Exhaust cards can get rid of art halves, and Left Brain can proc on all the Statuses. Distortion makes it even better. Also a fun interaction with Creativity, ripping a card counts as creating two for Makeshift Shord/Shield.

I can't remember the deck it came from, but any power that enables you to generate block when you create cards is very good. Tons of packs will "add a card to -----" or "exhaust, then add a copy ----" or "gain 6 block and add 2 ghost claws to your hand". Very powerful results that allow your deck to stay VERY aggressive.

I'm pretty sure Walock imps and Mass Production from Grand Legacy is a great combo (the duplicated imps don't increase each others' damage, but they still hit the ones in the deck). I abandoned it part way through for Mass Produced Ghostly Mists from Transmutation tho. It's super swingy and kind of whatever on average, but it's a lot of fun when it hits

alignment is pretty great with stall from the warden pack, and the entire flow pack

Flow mechanic and Quiet weights is a good combination, you can discard weighs really easy with flow

Cosmos Command and Distortion packs work really well together for the Distortion debuff. You have the strike + distortion from one pack and defend + distortion from the other pack, so they're good cards to use to replace your starter cards. They also have aoe distortion skills.

Then combine it with Alignment pack and other packs that can generate 0 cost cards that exhaust, you can have an insane run with it. As for me, I was able to get that from fertilizers (Farmer pack) and Porcupine (Summoner's Menagerie pack) that can generate quills.

And one final thing I had that made it even more satisfying is getting Spontaneous Ritual (Graveyard pack). Very good finishing move as it exhausts your whole hand.

One simple one I like is Quiet + Silent + some way to make energy. It's always a fun time. Another simple one is Graveyard and Warlock together can get very funny. Lastly, one of the longest turns I've had with this character was a result of having two Baalorlord's Bash and two copies of Chaos Vial. I would highly recommend doing so yourself if you have the chance.

Board games + Bardic inspiration is insane
Especially Perception check+Splendid form
Tripling the damage of an attack, that you have already increased with dice regularly puts it at 60 or so damage.

It should be noted, this is not the ONLY good combo with board games, sommoners menagerie has leprecaun(which is an extra d6 per turn, up to 3 without orb slot increases), Marisa(charge up mechanic, double damage), Aggression(1.25 times damage, also gains strength), Sentinel(angry 1.5 times damage)

also vulnerable generation and multi-hit moves benefit, I will not list all the moves this applies to here

This isn't a pack combo, but it's so ridiculous I just have to. The Energized pack goes suuuuper hard with Snecko Eye. It's insane.

Distortion (or any good Distortion generator pack) with Pixie pack

Originally posted by Bad Joe:

Then combine it with Alignment pack and other packs that can generate 0 cost cards that exhaust, you can have an insane run with it. As for me, I was able to get that from fertilizers (Farmer pack) and Porcupine (Summoner's Menagerie pack) that can generate quills.

Booster Pack adds 5 ethereal cards to your hand for 0. I also had added in a Spontanous Ritual, but the Booster Pack was what made it especially deadly.

Distortion Pack + Claw Pack is a surprisingly good combo. Cloak and Claw and Infinite Claws let you exhaust constantly. The Static card also is amazing with Mutate Claw.
This isn't a pack synergy but Static + The Boot goes hard and makes the boot actually worth grabbing at chests. Makes Static basically 5x better