The Tavern

I realize this is an incredibly niche and first-world question, but...

Why can't you Spectral Weapon the Sword of Power? I just get "the +27 Sword of Power vibrates crazily for a moment."

Technical reasons. The Sword of Power (and a few other unrands, like the Singing Sword I think) have mechanics that don't work with Spectral Weapon. Probably it could be done, but it would be a serious chore; it's much much easier to just ban them from being Spectralized.

ftfy

The "special" tag makes an unrand unwieldable by monsters (and spectral/dancing weapons are basically just monsters that are wielding themselves), and it's mostly used for unrands with effects that run every turn, since those are only implemented to work when equipped by the player. Examples: the Sword of Power and the Mace of Variability recalculate their pluses every turn, the Singing Sword has a chance of talking/dealing damage, the Sceptre of Torment has a chance of tormenting (on top of its 50% chance of tormenting when swung in melee, which would actually work fine in monster hands) - all of those, plus some others, are tagged as special. (Fun trivia: vault-makers can give monsters those unrands anyway, and someone did exactly this with the obsidian axe at one point when it was tagged as special, resulting in a monster which would summon friendly demons for you when it attacked).

The tag is semi-arbitrarily applied where it seems most important, since some other unrands with that kind of effect can still be wielded by monsters - for example the Scythe of Curses doesn't curse items when wielded by a monster, and the Storm Bow and robe of Clouds don't generate rain clouds.

I suppose Sword of Power with Spectral Weapon would either need to be special cased to use your HP or spawn in as +4 (Max HP on a Spectral Weapon is 44). +4 Great Sword isn't really that good.

Do spectral weapons even get enchantment?

This is pretty excellent; it's good that there's at least one item in the game that hates anything that wields it.

Obsidian axe demons are usually friendly to you if you are wielding it.

Yeah -- but the axe really wants to get players killed. It just summons some demons to laugh at you.

Thanks for the answers. I had thought it would just have whatever plusses you had when summoning it. It was disappointing to find out it wouldn't work after finally finding a book of battle!

FWIW, Sword of Power, Singing Sword, Mace of Variability, Sword of Zonguldrok, and probably a few others I'm overlooking are on this list. Generally speaking, if the unrand has an effect not seen on any other weapon, it's probably a candidate for not being Spectralized, although this is more a guideline than a hard rule.