[SixOfSpades]

Clarification on Link's post.

Open up baldur.ini in Notepad or something similar. Look for the lines that say "Program Options" and "Game Options." Write in "Debug Mode = 1" and "CheatKeys = 1" right after those lines.
(I keep forgetting if those are supposed to go under Program or Game options, so I just do both. Overkill still works.)

Then, start up BG2, travel to the Underdark Exit, and hit Ctrl-Space. This brings up a new little text bar, where you can type CLUA commands. You should say:
CLUAConsole:CreateCreature("c6elhan")
Make sure it is exactly as you see it above. Capitalization does not matter between the quotation marks, but it does in the rest of the command.
Then hit Enter, of course. Elhan will appear standing next to your main character. It might help if you do this right outside the door of a tent that's kind of near the bottom left of the screen, because that's where Elhan is supposed to be. Look around for some Elven War Sages, that's Elhan's tent.

Link, I got Elhan's creature code by looking up his CRE file in Shadowkeeper and ruling out the other Elhans that were probably not the correct one. Or did you mean a list of ALL possible CLUA commands?