So what is alchemy on site? I see some items have an alchemy tier, and when I read to my pet it sometimes gains a point in alchemy. The only thing on site I've been able to find is restricted to zombies only.

The alchemy points you can get from reading to your pet are used in the battledome, more specifically with scrolls. Each scroll have an AP cost, and you can only equip it to a pet with enough AP. So if you have a scroll that costs 25 AP you can only use it if your pet has 25 AP or more. Some examples of scrolls:

Now zombie alchemy is something completely unrelated. You can learn more about it here: