I want to open a portal to the Quasi-elemental Plane of Radiance that'll unleash a big ol' laser that'll probably ruin some monster's day. (Currently I'm considering using dimension door to do it.) Is this possible?
While a feature of earlier editions, the quasi-elemental planes go unmentioned in Dungeons and Dragons 3.5. However, the Dragon #321 article "The Limitless Light" (64-8) describes the Plane of Radiance, a coterminous plane equally the opposite of the Plane of Shadow, but that Plane of Radiance is actually very nice and not at all filled with lasers. (Manual of the Planes mentions quasi-planes (21)—they're the soft borders of multiple planes—, but the text doesn't mention any by name.)
Bringing stuff (instead of creatures) from one plane to another (e.g. flooding the Material Plane via an opening to the Elemental Plane of Water) probably requires the 9th-level Sor/Wiz spell gate [conj] (PH 234), which causes "anyone or anything that moves through [it to be] shunted instantly to the other side" (emphasis mine). Although that or anything is likely a rhetorical flourish intended to deter using the spell lest it accidentally bring forth, for example, Cthulhu, a generous DM may rule this means the possibility of, for example, conjuring a deluge of material from the Inner Planes while the opening exists and if the opening's properly oriented.
It's possible for a generous DM to rule that a magic item like the cubic gate (DMG 251) (164,000 gp; 0 lbs.) accomplishes the same effect, but since the opening is to a random destination on the plane, the opening is just as likely to be facing the wrong way to cause the desired apocalypse.