Instead of hit points, have it create a bubble which protects for a specific amount of time. There would need to be a time limit for how long the bubble can last, can’t last longer than X hours. Can only be used once per day.
That might be a good solution to offline raiding though. You play, store up zeal tokens, and activate the bubble to protect you while you are offline. It lasts 12 hours, then you can’t activate it again until the next day starts. Once the bubble is activated you can’t deactivate it. So no intermittent control, continuous only. So each day you are vulnerable to raiding for 12 hours and can be protected for 12 hours.
I like it! And it’s simple.
There doesn’t need to be a delay for its protection activating either, because if it protects for 12 hours and can only be activated once per day and it’s continuous, not intermittent. Then those who raid you can plan around it 12 hours later, if you activate it. Since it’s only used once per day, no abuse. Having multiple altars, could be solved by making them ALL activate if you activate one. So players can’t activate one, then another and so on. They all turn on at once, burn for 12 hours and then you’re vulnerable. Add repair hammer to see expiration time for bubble.
This is definitely the solution Conan Exiles needs!