Crawling Infestation works but it is not very useful, the range is very short, the AP cost is ridiculously high and it takes 3 or 4 turns to go through if not walked off by the enemy. But if it goes through, the infected enemy instantly dies and out of its corpse come 2-3 spiders, which join you in battle and that is actually pretty good but the chance for this to happen is really low.
