Highly acidic spiders are non-attackable Araxyte that are summoned by Araxxor during the third phase. They can be lured by the player(s) to Araxxor, where he will absorb them and his enrage level will increase. Doing this during this phase will make the final phase slightly easier. Five of these spiders can be absorbed by Araxxor; for each one absorbed, he heals 5,000 life points and his rage will increase.
Like acidic spiders, these spiders only spawn whenever the middle path is one of the paths available; if the middle path is closed, they do not appear during the third phase.
Each highly acidic spider contains 25 units of acid on the pool, so four will spawn in a solo fight if the middle path was open but not taken. If the middle path was taken, any leftover acid from the pool that was not drained onto the barrier will be sent into the respective amount of spiders needed. A pool with 26 units of acid left will result in Araxxor spawning two spiders, one containing 25 units and the other containing 1 unit.
It is a good idea to allow him to absorb them when he is almost dead, so the player is less exposed to Araxxor's enraged attacks.
Having Araxxi absorb all of the acid from the pool (this includes highly acidic spiders) is a requirement to unlock Bill.