One of the wonderful things about working with the X-Men was the access to the advanced alien technology they had received from the Shi'ar empire. Greg was still learning about it (and unlearning a few things he'd been taught in school). He'd used some of their tricks to build a portable, solid-state music player that could survive the ridiculous number of G's of acceleration that he could pull when flying.
Cruising along at Mach 8, he grooved to Lila Cheney's "High Up", a song about a fighter pilot obsessed with flying. One of the reasons he liked her as an artist was that she didn't just write the same old songs about love and breakups and such. And when she did, they tended to be from a different angle - kind of like the Barenaked Ladies, only a lot grittier.
This was a song he could relate to. He wasn't actually addicted to flying (or at least, he didn't think so), but there were few things in life more fun.
{Like, for example...} Greg smiled as he remembered the make-out session he'd had with Rogue after his training session. The term at UW would be over in just a few more weeks, and he'd be transferring to Xavier's school. At the speeds he could move, Wisconsin wasn't that far away, but being next door was better than several states over.
{Besides, I can keep better tabs on things from there.} Being away a lot of the time, he usually only found out after the fact about the amazing troubles the X-Men tended to land in. Like that crazy Asgard mess. He was in an unusual position; too old for the New Mutants, but lacking enough training to be in the X-Men.
He wasn't entirely sure he wanted to be an X-Man, either. First, of course, he was normally rather prudent about his safety, and his only official outing with them had very nearly gotten him killed. Second, while he thought encouraging amicable mutant-human relations was an admirable goal, he wasn't at all certain that it was possible. Incidents of hate crimes against mutants and increasingly strident posturing by politicians didn't help his attitude much.
Rogue was a believer, though, and if she was going to be putting herself in danger, Greg at least wanted to be around to help.
...while in many ways Greg would seem to be an ideal candidate for membership in the X-Men, I still have my reservations. He has many strengths, but his weaknesses cannot be ignored.
He seems to have had a stabilizing effect on Rogue. Their affection for each other is strong and genuine (I, at least, can be certain of that) despite the stresses of their unusual situation, and she has never seemed happier. Greg does seem to bring out a possessive streak in her, though.
Provided he is given time to think, he is capable of devising creative, if unorthodox, solutions to a problem. He has a tendency to lose this flexibility under pressure, however.
His powers are formidable, both offensively and, of course, defensively. His physical strength lies between that of Rogue and Colossus, but that is deceptive, as it derives from his field, and not his actual muscles. He can lift 60 tons over his head with one finger; but he cannot do better with both arms.
His ability to extend and reshape his field allows him to direct his power in ways that Rogue and Colossus cannot. An ultrasharp blade applied with tons of force is a dangerous weapon; indeed, I feel he will need significant practice to be able to apply it safely. Unlike Phoenix's telekinesis, however, he cannot act through walls.
His flight speed is staggering; simple calculations show that 60 tons of force, applied to 175 pounds, leads to accelerations in the hundreds of gravities. Of course, he cannot really reach his peak speed in atmosphere; power must be diverted to deflecting shockwaves. Still, perhaps only Northstar could hope to match his speed.
However, his reflexes are human-normal. A touch above average, but he is nevertheless among the slowest fighters here. He is easily capable of flying faster than he can safely manage. This is a solvable problem (c.f. Cannonball) but currently one of grave concern.
It is well that his defenses are so strong, since his relatively slower reflexes mean he cannot easily dodge many attacks. His field provides excellent protection from a wide range of phenomena; cautious testing has shown him proof against electromagnetic and ionizing radiation, extreme impact, heat, cold, acid, etc. Moreover, the field is active almost constantly, he does not need to invoke it.
It has proven of at least some utility in defending against more unusual attacks, as well. To affect him, one must penetrate or bypass the field; but to weaken the field requires affecting him. Since it normally extends at least a few micrometers outside his skin, he has proven immune to Rogue's power. It offered some protection against the Genoshan power-damper called "Wipeout" as well.
Of course, he is not utterly invulnerable. Enough force can penetrate the field. Unlike Colossus, he needs to breathe; gas-borne attacks may often be effective. In addition, his field is an insulator; he can prevent heat from reaching him, or reduce outward heat flow if, say, immersed in liquid nitrogen. But if the temperature outside his field is higher than his body temperature, he cannot pump the heat away. Surrounded by fire too long, he will collapse from heat prostration.
The most fascinating property of his field is the limited mental protection it provides; even I frequently have great difficulty reading more than his basic emotions, and psychic attacks are blunted. It would seem this effect is why Cerebro never detected him until he presented himself. Additionally, his will is unusually strong (no doubt partly due to the excercise it gets manipulating his forcefield). It is ironic that someone so well-protected nevertheless has a nearly pathological fear of mental manipulation.
From what Greg has shared with me, the psychic assault he suffered from the "Genoshan" interrogator was brutal. Indeed, the man was so needlessly sadistic that he failed to take sufficient care in his own defense; that and good luck are what allowed Greg to escape.
It left him scarred, with a deep, reflexive distrust of all psychic phenomena. It was only his overriding fear of another mental attack that persuaded him to allow me to help train him in psychic defense. Even that was done reluctantly, but he has been an extremely motivated pupil. At this point, with his field, his will, and the training I have provided, he is quite possibly the most difficult mental target of any non-psychic I have experience with. Any mentalist who attacks him will be in for an unpleasant surprise.
But here is the key weakness, the primary reason I hesitate to place Fortress among the X-Men. If attacked mentally, he will resist with his entire being, with no regard to other priorities, and with no moral reservations whatsoever.
One risk is to Greg himself. His defenses are substantial, but should a powerful psychic breach them, I worry that his self, his ego, would not withstand the shock. Little of him would remain. It is doubtful he could be beaten at this point; but he could be broken, shattered irreparably.
The other problem is that, in defending himself, he would almost certainly wreak unimaginable destruction on his assailaint, and anything or anyone that comes between them. I do not believe he is capable of making rational judgements in such circumstances. Even the threat of an attack may cloud his reason...