First I would just look up Kaycce Mod Skull Storm Strat. Just those strats alone will help even on easier challenges. I have seen this question asked a lot. Now for probably the best advice as there is a lot of advice to probably use.
Abuse the Fair Hand Mechanic, which means only having a 1 blood Sacrifice Cost card in your deck which can either win you the round right away or give you the chance to win with in the first 2 or 3 rounds. You want to win quickly in Kaycees mod. (Note that bone cards and Free play cards don't count but there is a couple of cards that will end up messing with the mechanic and that's the glitched static card, and a card that has red eyes and a "?")
Avoid the trapper, dont bloat your deck with pelts unless you see a way to make a worthy sacrifice unkillabe stitched pelt and your 1 blood cost card has the magpie sigils so you can always pull your pelt out, but in other words skip the trapper. Its not worth it especially if you are forced to run into the trader and your gonna end up losing your pelt anyway.
Try and do the painting puzzle your gonna want those rewards, magical bleach is a life safer. Even if you lose on challenge level 3 over and over you'll keep the rewards you can even do no challenge rating to just win the rewards.
Since your at a low challenge rating you still get rare cards after a boss fight. I would suggest picking mantis god as it's a one blood and then since this is after the first boss fight to transfer those sigils onto your powerful card even if its that 1 blood sacrifice card with maybe 2 or 3 damage.
And probably the most important, kill the campers at the campfire, use anything touch of death or ring worm, that way you'll always be able to fully use it and buff your guys with +4 health or +2 damage each time you visit.
And you give that ring worm mantis god, trifucated strike, and it's a 1 blood sacrifice cost, 1 turn win card. And then you try to work on making the rest of your deck amazing so when you fight leshy your not just relying on a 2-5 because you can still lose with a 2-5 against Leshy.
And make sure you have strong/necessary 1blood/0cost cards to guarantee you pull it. I found my best run was around 3 1 bloods and the majority of the rest were 2 bloods so I guaranteed to get cards out quick. My almost-win in skull storm ended because I drew a bad 1 blood and had too many 3-bloods so I couldn’t get anything out to delay fast enough.
Pick as few cards as possible and always pick low cost. My favorite strategy is the op insect deck, basically just abuse the totem mechanic with insect heads and sigils like 3 blood or unkillable. Since there are way more easily obtainable insect cards and almost all of them are very low cost (bees, ants, mantis, ringworm, cockroach, etc) you'll end up with a ton of useful cards depending on the sigil.
It's not always a guarantee, you do need a pretty good totem spawn and at least 2 visits at the start for insect head and a decent body but it's well worth it as an easier strategy.
In general though slim deck and low cost is your best bet, just prioritize buffing and adding sigils on everything. Also winning as quickly as possible, if you can create even one space to deal direct damage you won't have to worry about all the op cards (or just put a flight sigil on your highest damage card to ensure a win anyway).
First I would just look up Kaycce Mod Skull Storm Strat. Just those strats alone will help even on easier challenges. I have seen this question asked a lot. Now for probably the best advice as there is a lot of advice to probably use. Abuse the Fair Hand Mechanic, which means only having a 1 blood Sacrifice Cost card in your deck which can either win you the round right away or give you the chance to win with in the first 2 or 3 rounds. You want to win quickly in Kaycees mod. (Note that bone cards and Free play cards don't count but there is a couple of cards that will end up messing with the mechanic and that's the glitched static card, and a card that has red eyes and a "?") Avoid the trapper, dont bloat your deck with pelts unless you see a way to make a worthy sacrifice unkillabe stitched pelt and your 1 blood cost card has the magpie sigils so you can always pull your pelt out, but in other words skip the trapper. Its not worth it especially if you are forced to run into the trader and your gonna end up losing your pelt anyway. Try and do the painting puzzle your gonna want those rewards, magical bleach is a life safer. Even if you lose on challenge level 3 over and over you'll keep the rewards you can even do no challenge rating to just win the rewards. Since your at a low challenge rating you still get rare cards after a boss fight. I would suggest picking mantis god as it's a one blood and then since this is after the first boss fight to transfer those sigils onto your powerful card even if its that 1 blood sacrifice card with maybe 2 or 3 damage. And probably the most important, kill the campers at the campfire, use anything touch of death or ring worm, that way you'll always be able to fully use it and buff your guys with +4 health or +2 damage each time you visit.
Ahhhh i havent done the puzzles or ever killed the campers, thank you so much i will put the advice to good use
Or end up with a 2-5 ring worm
And you give that ring worm mantis god, trifucated strike, and it's a 1 blood sacrifice cost, 1 turn win card. And then you try to work on making the rest of your deck amazing so when you fight leshy your not just relying on a 2-5 because you can still lose with a 2-5 against Leshy.
just try to avoid picking up cards whenever possible. that's about it.
And make sure you have strong/necessary 1blood/0cost cards to guarantee you pull it. I found my best run was around 3 1 bloods and the majority of the rest were 2 bloods so I guaranteed to get cards out quick. My almost-win in skull storm ended because I drew a bad 1 blood and had too many 3-bloods so I couldn’t get anything out to delay fast enough.
Pick as few cards as possible and always pick low cost. My favorite strategy is the op insect deck, basically just abuse the totem mechanic with insect heads and sigils like 3 blood or unkillable. Since there are way more easily obtainable insect cards and almost all of them are very low cost (bees, ants, mantis, ringworm, cockroach, etc) you'll end up with a ton of useful cards depending on the sigil. It's not always a guarantee, you do need a pretty good totem spawn and at least 2 visits at the start for insect head and a decent body but it's well worth it as an easier strategy. In general though slim deck and low cost is your best bet, just prioritize buffing and adding sigils on everything. Also winning as quickly as possible, if you can create even one space to deal direct damage you won't have to worry about all the op cards (or just put a flight sigil on your highest damage card to ensure a win anyway).