Anval Thawn (not to be confused with Grand Admiral Thrawn of Star Wars fame) is a Terminator Justicar of the Grey Knights and a distant relative of Jesus Motherfucking Christ. He is also immortal, which in 40k isn't actually that significant. He was pulled off the infamous Black Ships, and ever since has gone on to troll daemons left, right, and centre, normally dying (temporarily) in the process.
Marty Stu or not a Marty Stu?
While Thawn does have many Mary Sueish traits, he's not really a Marty Stu, because his Manliness saves him from it. As it says in the Grey Knights 'dex, he finds immortality a curse. This means that he cries manly tears while he tries to stop the Imperium from turning to shit BUT FAILS.
On the tabletop
On Tabletop, Thawn is basically a normal Grey knight terminator Justicar with a halberd, except for the fact he's mastery two, has odd grenades no-one even noticed and comes back from the dead on a 4+. He is mostly useless, except as a last turn objective denier/linebreaker. This works better against armies with high-cost units, as they often can not afford to babysit him (in smaller games.) He is however 75 points. It is also worth knowing he does allow use of both hammerhands and force weapons, useful against some armies.
Future of Thawn
It is worth bearing in mind that, while at the moment he cries about the shitpit the imperium is and makes chaos roll for Anal circumference, he does have many prophecies laid out for him to follow. One such prophecy states that when Justicar Thawn falls for the last, it will be protecting the EMPRAH. However, due to Games Workshop's inability to move the plot forward, it is unlikely we will ever know for sure. It's also possible he's just a result of Tzeentch's assmongering*BLAM*. Thawn is untaintable and is safe from all dark powers by some crappy Ward rule that is definitely not overpowered.
Spoiler, he's a Perpetual; the last one, in fact, and the Eldar know about him.
Notable Achievements of Justicar Thawn
- Leading a charge against Ku'gath plaguefather, a great unclean one.
- Cutting out of said daemon's stomach after having been swallowed.
- Being the last known Perpetual.
- Being killed by a binging (on soulstones) Keeper of Secrets to save a grand master.
- Surviving (or maybe dying and resurrecting a lot) against all the bad shit on a daemon world by himself for a week.