Protecting cc troops from poison spell
Troops in your clan castle still serve a valuable purpose, even if they can be killed with a poison spell.
- It makes the attacker spend at least one spell slot on poison.
- It makes the attacker spend valuable time drawing and poisoning your CC troops.
There are a few things you can do to make poison less effective.
- Put your clan castle in the center of your base so it's harder for the enemy to draw your troops out.
- Don't put your skeleton traps near your clan castle. You don't want all of your defensive troops to die from poison (or from attacking troops) in one big group. Spread them out as much as you can.
- Know which clan castle troops can survive a poison spell. The longer it takes the poison to take effect the better. I like a dragon in my CC, but they're expensive so I usually only ask for one during a clan war. PEKKA are good too, but they're also expensive. High-level giants and valkyrie are good because they last a long time against poison (or attacking troops) and they don't cost as much as other high-HP troops.
There are 2 more things I thought of that weren't mentioned by other posters.
Troop Speed - put troops with different speeds in your CC, so they don't group up as easily in the poison spell. One example would be to put some faster troops like valkyries in with some very slow troops like balloons.
Lava Hound - Admittedly, not available at TH8; however, once you get to TH9, the best thing you can get is a lava hound, since they are very tanky and spawn a bunch of obnoxious pups when they die, they are the best thing to have in your clan castle at the moment. However, due to their high dark elixir cost, they are probably only regularly affordable during clan wars, or as special requests.
Most things in the game have a counter (ie, PEKKAs are weak to tesla, barbs/archers are weak to mortars), and it just so happens that the poison spell is the counter to the clan castle.
There's not much you can do to protect yourself once the castle troops are out. What you can do is attempt to put your castle in a spot where it's hard to pull the troops out. Try to centralize the clan castle so that it takes a significant amount of deployed troops to destroy enough of your base and get your guys to come out.
This can spiral into other areas of your base design if you try to protect against, say, a hog rider pull. If you put anti-hog defenses (ie, giant bombs) near the side of your base nearest the clan castle, you can play mind tricks on your attackers while they try to pull your clan castle troops.
I've found, however, that most of the time my attackers are pretty "unprepared" and either don't bring poison, don't bother to pull the clan castle, or just forget completely about it. I know most of the bases I raid don't have clan castle troops to begin with.