Typhon, the deadliest monster in Greek mythology, was also the father of Orthros.

Monster formations fought only in the coliseum don't appear on the Beast Plain, so Gau can never legitimately learn this rage, though it's nothing special anyway. Note that because monsters select randomly from their control command list when appearing in the coliseum, you'll get blown out of combat quite often.

A reference to FFIII's Onion Knight?

For something that's supposed to be armor, these have strangely low physical defense.

Gau has this Rage already learned when he initially joins the party.

Hroþgar SCRB notes an apparent connection to "spritzer", a drink made from white wine and carbonated water, which comes out as スプリッツァー in Japanese. It makes as much sense as anything. Regardless, the use of ピ (PI) instead of プ (PU) to evoke "spirit" appears to be deliberate.

This looks like another name with reversal. アイノゲロ (AI NO GERO) could roughly translate to "barf of love", though ゲロ could also be a frog noise.

Shouldn't "due to" be ドゥトゥ DU TU rather than ドゥドゥ DU DU? Probably, but Japanese renditions of foreign terms tend to play fast and loose with phonetics, and when said quickly, the phrase often sounds a lot like "du də" anyway. Regardless, it sort of fits with the creature being undead, and the Japanese Final Fantasy glossary wiki also supports this interpretation.

More accurately, サボテン means "cactus", and ダー roughly sounds like 'dar', but "Cactusdar" doesn't really flow very well. There's also been speculation that it's a portmanteau of サボテン and プリテンダー (pretender), suggesting that it's something that's only pretending to be a cactus. I'm suddenly reminded of the Pokémon Sudowoodo, which is actually a rock despite looking like a tree.

Given the absurd defensive and evasive stats, you'll want something unblockable, and preferably defense-ignoring, to kill these things. The formation gives massive amounts of LP, making it well worth the trouble. Several characters have appropriate skills, such as Edgar's Drill. Setzer's Dice and Fixed Dice also work particularly well, since they're innately unblockable and always inflict a minimum of twice the user's level in damage.

Possibly in reference to highwaymen, bandits (usually on horseback) who would rob travellers along public roadways. This is also one of those monsters with a completely unexpected and out-of-place Sketch result, and the Rage skill doesn't make much sense, either.

Possibly named after Nara Camicie, an Italian line of designer clothing.

And in the running for Most Pointless Censorship, we have "hades" replacing... "hill"? I suppose NoA's policies made people a bit paranoid.

That Carving Knife is brutal, inflicting eight times normal attack damage. Unfortunately for Gau, the Rage gets the relatively boring Break instead.

Look at all those status immunities and elemental absorptions. Throw in Curega and you have an amazing defensive Rage.

Their extreme magic defense and very high physical evade were supposed to make these difficult to harm, but the evade bug largely ruins that.

Hroþgar SCRB notes that デボア matches the Dutch name "De Boer". Further searching finds that ハーン also matches a Dutch name, "Haan". Why this creature would have names from Dutch eludes me, but it makes as much sense as anything.

Spanish for "scorpion". I think might have noticed that already when I first did the name, but just didn't leave a note about it or use the acute mark at first.