Captor Spider is a Shadow that the Clockwork God uses to monitor the party's actions. Once Zen fully restores Rei's memories, it is deployed as a swarm of Shadows in order to forcefully take her to the Sea of Souls alongside Zen.
It is later confronted on top of the Clock Tower and defeated by the party, freeing Rei. This prompts the Clockwork God himself to take action so he can annihilate the party and force Zen to merge with him.
Strategy[]
The Captor Spider is relatively straightforward. Simply attack away at the head until it retreats behind its legs. If it launches a normal attack, it hits four random targets amongst the party. Once it retreats and raises its legs, each leg will then take their action individually, either with a normal attack or a -dyne spell.
For the purposes of conserving SP, have party members equip weapons that deal elemental damage to get free Boost status for more devastating area attacks. Agility Bind is still effective the Spider and its legs, so don't neglect them - cutting their accuracy means fewer chances of losing Boost due to getting hit and fewer turns spent healing off the damage. More importantly, because the Spider is immune to every status ailment other than binds, Agility Bind is the only way to ensure that attacks such as Myriad Arrows strike the Spider.
After all four legs are destroyed, the Captor Spider falls forward and is helpless for a few turns, allowing the party to freely attack it. After a few turns, it will regenerate its legs and retreat behind them. Attacking the Spider in such a way that all four of its legs die at the same time is a good way to optimize the party's damage outputs.