summoning towers are large metal towers that resemble electrical transformers and radio towers. the primary purpose of the summoning tower is to contact the spellbinders when they are needed. an eyestone is placed into a cradle at the base of the tower, which presumably amplifies the signal it generates. the summoning towers also produce a magnetic field used to give flying ships their 'lift' (as evidenced when paul shorts the main power stone in the castle, causing all flying ships to crash) and can be used as a landing pad for the flying ships.