Third Space Aliens From Babylon 5 In Star Trek

[Demiurgas]

We know the First Ones, from Babylon 5 can equal Borg/even perhaps Undine (Species 8472) levels of power. Knowing this, how powerful and influential can the Third Space Aliens from Babylon 5 be in Star Trek?
http://en.wikipedia.org/wiki/Civilizations_in_Babylon_5

The Vorlons, a race of First Ones, could not defeat the Third Space Aliens by themselves.

[Juubi Karakuchi]

The Thirdspace Aliens are essentially the Cthulu tie-in for the Babylon 5 universe, so they have the potential to be very dangerous.

The information I have on the Thirdspace aliens, or the 'Harbingers' as they are also known, comes from Bryan Steele's sourcebook on them from Mongoose. The beings themselves are jellyfish or squid-like monstrosities, using mental powers to move around. They have some ability to manipulate their own bodies, and can also manipulate matter. Their bodies are physical and need to eat, which seems to be the main reason why they invade other dimensions.

When invading other dimensions, the Harbingers start by using their mental powers to subvert the natives. Cultists are seduced with visions of paradise, usually of a 'black city' in which all beings will live in joyous servitude. The sourcebook divides Harbinger cultists into two categories; servitors and devout (p. 63). Servitors are under mind control by the Harbingers, and only appear when the Harbingers are near (whether in their dimension or attempting to enter it). The devout exist at all times, whether as servitors who continued to worship the Harbingers, or as followers of Harbinger-worshipping religions developed over millenia. The role of the cults is to help the Harbingers open a gateway, the method usually involving human (etc) sacrifice. By such means they will generally summon a single Harbinger, which will then set about the work of summoning more. When enough have been brought through, they will create a gateway to bring the rest through en-masse. It takes hundreds of Harbingers working together a century or more to manifest a Thirdspace gate (p. 67).

There isn't much transferable information on Harbinger warships. Like all their 'technology', their warships are 'metapathically' created semi-living constructs (p. 56). Harbinger shields are described as being a 'meta-scientific cousin of photosynthesis to produce a tangible wall of ambient energy.' Personal generators can cover an area up to 10 feet tall or wide, absorbing 20% of incoming damage. Starship generators vary according to ship type. Architectural generators absorb 90% of damage. Shields need to be powered by Energy Re-Doublers, which draw upon and magnify local power sources into infinite sources of energy (p. 58). Cherubim 'frigates' and Nephilim 'destroyers' are unmanned constructs, programmed to seek and destroy. Seraphim 'dreadnoughts' are larger and more powerful, piloted by the Harbingers themselves. The largest vessels are the Throne 'gateships', described as 'spikes or spears roughly three miles long,' numbering a few dozen at the most (p. 61). A Throne can act as a gateway in its own right. Cherubim are described as being a match for four Younger Race ships (p. 30).

[Demiurgas]

Interesting, but kind of disappointing. Four Younger Race Ships aren't much of a match for 1 Star Trek vessel.

[lord Martiya]

Those are the small ships. A small ship that's a match for four Omegas? I fear the big ships...

[Batman]

Thirdspace fighters could be taken down by Starfuries with some effort so I doubt they're that far beyond YR capabilities-wise.

[Rekkon]

I will have to go watch Thirdspace again, but I do not seem to recall seeing any of the small ships getting destroyed by Starfuries. There is that one scene where a Fury basically parks next to one and blasts away until his target swings around and blows him away, but the Thirdspace ship survived that. One pilot reports to Ivanova that they need to hit them four times before they even notice. That sounds pretty ineffective. Even White Stars did not look like an even match, and there were several scenes with Sharlins that had the crap kicked out of them.

[Batman]

No you won't because you're right, I was mistaken-while mainly the White Stars and Sharlins fire at the artifact there's a few scenes of White Stars firing at the fighters, and while they manage to kill them, it takes them upwards of a second to do so, indicating those things are considerably more resilient than YR stuff, possibly due to apparently having shields.
Radio chatter from an unnamed Starfury pilot mentions they can barely hurt them, intimating that they can hurt them with sufficient effort, but I don't think we ever see that happen onscreen.