So I think the Spidicules is a good fight, and don't have any strong critiques of those mechanicas, and some of the gear fit well, but I'm going to detail some of the things that have been bugging me.
My main complaint is with the instruction use as a replacement for the Antelope. While this is a fine idea, and conceptually adds a good amount of variety to your campaigns, it's not thoroughly integrated and it just makes the expansion feel incomplete if it's supposed to be a replacement.
I think having taken occur every year is a little harsh and really gives you pause when deciding whether to confront L2 and L3 Spidicules early, not to mention slowing endeavor, age, and weapon proficiency advancement. I think it would work a little better to have it occur on the first encounter, and then maybe a 50% chance to occur on successive hunts.
I'm fine losing out on gear available at the Stone Circle.
that makes sense and maybe missing a few gear recipes in some other locations.
But you lose out on the all but one of the Barber Surgeon items.
You lose out some of the campaign specific items in the People of the Sun (not sure about some of the other variant campaigns, but this is the one where i tried Spidicules first)
You don't have access to the hybrid armor sets
No legendary variant, unless i've overlooked it
No replacement mask
No replacement cooking recipes (makes cooking just a +1 survival card)
Sure, I can come up with a couple of substitutions, but these are integration details that should have been thoroughly examined if it was intended as a monster replacement. It's just annoying that you lose so much content by swapping the antelope with the spider, because i think it is a fun fight that's decently challenging in a different way. Maybe if the gear was stronger or offered some sort of advantage compared to the content you lose, then it would be a fair trade, but as written, it misses the mark.
Current solutions/substitutions i've identified is to use the Stomach resource for the Bladder on the Ring Bow (Sacred Pool) and The Weaver rare gear as a replacement for the legendary horns in the Apostle Crown (Sacred Pool). I could stand to lose out on either the Barber Surgeon or the Cooking events, but not both. The distribution of spider resources is a little odd, but haven't completely compared it to the Screaming Antelope resources to see what are suitable replacements.
I just use the rules for adding Spidicules to a current game. You don't replace Endless Screams of you do this. There's really no reason that I know of to actually replace the Screaming Antelope.