Planejammer Campaign Setting
Spell Hooks, Bubbles, and Crystals
There are many spells that allow casters to contact or summon beings on another plane. When you are the one on the other plane you can see a visual representation of these spell effects, and may sometimes run afoul of them.
While on the Inner Planes conjuration and summoning spells appear as Hooks. A hook appears most often as a glowing spear, grappling hook, or shepherd’s crook hanging in mid air. Targeted creatures are drawn to these hooks by an effect similar to a charm spell.
If a non-native touches a hook he or she will need to succeed a will save as though vs. a charm spell of the same level. Failing the save means that character is affected as though it were the target creature, being immediately transported to the Prime Material and suffering the same strictures as any other summoned creature. On a critical failure the subject is whisked away to a random portion of the Deep Ethereal.
Contact Other Plane spells and similar magics appear as Bubbles, large silvery spheres that can range from 1 to 10 inches in size. It breaks at a touch, and the question contained within pops into the mind of the one who broke it. The being can then respond but the caster will be aware that the source of information is suspect.
On the Outer Planes Spell Crystals represent magics that contact or summon creatures. The effect of each individual Spell Crystal can be determined with a spellcraft check (DC = 25 + Spell Level + Caster’s Ability Modifier). Planewalker’s should be advised that Spell Crystals can contain anything from harmless divinations to conjuration and summoning magics.
From AD&D Manual of the Planes