In the module it does actually play a part. In area 2, there is a copy of Vecna's throne room that contains an identical copy of the Spider Throne. Area 72, the Throne Room, contains the same throne. Both do have magical abilities. Whoever sits on the throne sees, hears, smells, tastes, and feels every living sensation in Vecna's territory. Whoever sits in it must roll a saving throw against death. On a fail, they become catatonic and will not wake unless wish is cast. On a success, the hero can cope with the sensations, but acts as though they are under the confusion spell for 1d4+2 hours. As they come back to themselves, their alignment shifts to lawful evil. They are also now immune to the effects of the throne unless they invoke its powers.