Marine codex 'review' (#3): little brothers.

Librarian: great.

Weighing in at a 100 points, the librarian doesn't look like much.
At first glance, he seems incredibly weak, with a statline identical to chaplains, and much, much weaker gear than all the other options.

First glances, however, rarely manage to take in the full package.

Those 100 points actually buy you McGyver.

Librarians are psykers, and very good ones at that. Unlike most other armies, your psykers bring very real, very useful, envied support, dangerous offensive spells, and a couple odd ones.

Avenger, smite, and vortex of doom are offensive spells. The first is a really powerful flamer, smite is multi-shot finger lightning with AP2, and the vortex is a strength 10, AP1 blast, that's also a heavy weapon. It's worth mentioning that all these have very limited ranges.
Nullzone and force dome make up your support, with the first one forcing re-rolls of all successful enemy invulnerable saves within 24 inches (must-have), and the second giving the librarian and any unit he's with a 5+ invulnerable save.
The odd ones are machine curse, (the) quickening, might of the ancients, and the gate of infinity. Number one is the oddest, counting as a ranged attack, with a hit inflicting an automatic glancing hit on any vehicle it's targeted at. The second and third powers are buffs, giving the librarian fleet and initiative 10, and making him count as a monstrous creature with a strength of 6 respectively. The gate allows you to pick up the librarian, as well as any unit he's attached to, and redeploy them anywhere within 24 inches, counting the whole thing as a deep strike, with the funky drawback that a double on the scatter means a single guy in his unit will die.

It's possible to go into great depth and detail for all these powers, but that's reserved for the truly good ones.
Of importance is that while librarians have a lot of options, they are only ever allowed to bring two spells into battle, and can only use a single one per player turn.

Spells are good to have, yes, but ninja magic is better, and librarians get four to pick from. These are, in order from most potent to least, nullzone, avenger, gate, and force dome.

The presence of nullzone screws over most elite infantry. Forcing re-rolls equals less shots and blows necessary to down a given target. This is extremely potent, and means your small, compact army can down hard targets with less guys shooting and cutting them, freeing up resources to kill more stuff in any given turn that nullzone goes off. Easily the best ninja magic available to space marines - if not the best ninja magic in the entire game.

Since all offensive spells are so short-ranged, if you pick any of them, you want it to be the most useful, powerful, and reliable, so the chance of leaving survivors goes down. The avenger is the ninja magic you seek.
Being a flamer template, it ignores cover saves, and since it's AP3, as well as moderate strength, it toasts most heavy- and all light infantry. Handy bonus: shooting avenger from a rhino hatch gives you that bit extra range.

Gate lets you redeploy, effectively covering vast distances without a transport or letting the enemy shoot you before you're in their lines. Because it's a deep strike teleport, placing the librarian and his unit near locator beacons means you won't scatter.
This is a nice thing to have, and can be used to move around large, shooty units very quickly.

Force dome makes non-terminator units in the open and assault a lot more durable, and can shift some combats in your favor.
This power is a lot more useful than most think, but it's not as good as the other ninja magic at your disposal. Despite this, it occasionally becomes game-changing, allowing important units to stick around for another turn.

Librarians aren't all spells, though, and pack force weapons and psychic hoods. The first is a glorified power weapon that lets you execute a special instant-kill spell if you inflict damage to the target. Unfortunately, this spell counts towards your 'once a player turn' allowance, so is rarely used.
'Hoods are one of the game's few and far between psychic defenses. Keeping a librarian within 24 inches of enemy psykers gives you a fair chance of dispelling their spells and ninja magic.

Option-wise, librarians have a lot of useless stuff (all guns bar one, jump pack), some useful stuff (terminator armor, bike, combi-melta), and a very expensive one (terminator armor with a stormshield). If you want to use vortex of doom, or just increase your durability, investing in terminator armor or a bike is essential. Terminator armor also lets you deep strike, and you're right at home with other terminators, without being a total liability.

Because space marines are special, their psykers can pay a silly amount of points to be allowed usage of two spells a player turn.
This is a bad investment, thanks to the fact you get half of a second librarian for the points, and you'll rarely need to use two powers a turn, anyway. Some 'combat' librarians splash points on this, relying on the unreliable 'durr, hurr! funny'-combo of buffs and force weapon to 'assassinate' characters. It's not a smart thing to do.

All in all, the most useful HQ you can field, and at a budget price.
He won't butcher armies on his own, but his presence means the rest of your army will have an easier time doing so, and the librarian himself offers hard-to-find protection against enemy psykers, as well as an unreliable insta-kill - which sometimes comes in handy.

Because of all these things - nullzone in particular - librarians are almost a must-have. Much like captains, librarians make any army you could ever think of better, but unlike captains, they don't cost much of anything to include.

Should almost always be your default HQ.

What makes it good: utility unit. Brings very potent ninja magic, as well as defense against enemy psykers. If geared for it, has very powerful - if short-ranged - offensive capabilities. Very flexible and reliable. Hands down the best HQ available to space marines.

What makes it bad: fragile. Librarians are the least durable class of character you can field.

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Chaplain: bad.

For 100 points, and coming off the librarian, you'd expect a lot more.
Chaplains are generally bad investments, because the units they're normally attached to are either still bad even with the chaplain supporting them (assault marines, vanguard), or so good in the first place, the chaplain's powers are almost meaningless (assault terminators, command squads).
Still, he's got some good gear. Like librarians, chaplains start out almost fully kitted, with both a power weapon and an iron halo-equivalent. What this all means is, he's slightly more survivable than a librarian, but actually less killy on his own, due to a distinct lack of ninja magic.

In addition to his limited combat prowess, weak stats, and good gear, chaplains make any unit they're attached to fearless - which is bad - and on any turn they charge, every dude in the unit gets to re-roll missed hits.

If you feel like blowing more points, you can 'upgrade' him with some stuff; terminator armor, jump pack, bike, a powerfist, the uselessly useless plasmapistol, and guns. Not counting the powerfist, it's all kinds of lame and stupid, honestly.

It's fair to tell you all that during the days of 3rd edition, chaplains were the only HQ worth fielding.
Now they've been reduced to the only HQ not worth fielding.

What makes it good: good starting gear.

What makes it bad: chaplains have the dubious double honor of being HQ units that do nothing truly special for the army as a whole, and easily being the worst possible HQ a marine player can put on the field. No, the presence of a chaplain doesn't turn assault marines into actual combat units. Is quite obviously not a librarian, yet costs the same amount of points, and consumes the same slot.

-

Master of the forge: good.

A shooty boss, costing 100 points base.
One of the rarest species in the game, and he's quite a specimen.

Outside of tau, there are few heavily armed shooting characters, and this is one of them.
Straight ouf of the box, he gets artificer armor, a flamer, linked plasmapistol, and two powerfist attacks. Nice, flexible, and cheap.
That's the name of the game: flexible.
On the field, forgelords are generalist HQ's, capable of torching infantry, tanking some damage, hurting armor, and beating up stuff in combat. In any given turn, he's almost guaranteed to be killing something, or getting killed to spare more critical pieces of your army.
This isn't the main reason why you brought him, however.

In addition to his weapons and bling, the master of the forge lends you the power to take dreadnoughts - of any type - as heavy support, as well as elites. Six dreads max? Oh my.
He also boosts the cover save conferred by a single ruin in your deployment zone, and can repair vehicles in your shooting phase. The boost is useful, but repairing less so, since it costs you his shooting for that turn.
Unlocks a unit we don't talk about in public.

He's not exactly starved for options, either, having access to a bunch of mostly useless guns, digi-weapons, bike, and picking a thunderhammer or a power weapon. The only guns truly worth it are, of course, flamer and melta combis. For added flexibility, the power weapon is usually a good buy, and the hammer is sometimes useful.

If you trade in all your starting weapons, you can buy him a really big and silly gun. If you do this, the bike becomes almost mandatory, at it allows him to move and fire.
In the grim darkness of the far future, some guns increase in power the farther away the target is, and the conversion beamer is such a gun.
At short ranges, your gun's profile is almost nothing. Medium range, it increases dramatically, but still isn't all that good. It's at long ranges that this thing becomes deadly, plonking down a strength 10 blast, with AP1, but unless you've given him a bike, he won't get to fire at maximum effectiveness that often.
There's still some debate over whether or not he keeps a servo-arm in this trade, but what people fail to realize is how unimportant and useless the debate is. If he's got the big gun, he's not gonna go anywhere near the enemy, ever.

In short, he either helps the infantry out up close and personal, or hangs back to destroy armor and elite infantry.

Very good value for the points, and has massive presence on the tabletop.

What makes it good: utility unit. Fielding one lets you take more dreads, fortify a ruin, and repair vehicles. Generally a useful character to have, thanks to his wide and varied range of equipment. The second most potent class of combat character available to you. Conversion beamer is very powerful at long ranges.

What makes it bad: truly a generalist. Not as good at support as a librarian, not as killy up close or in combat as a captain/master, and not quite as durable as a chaplain or captains/masters. Has no invulnerable save, at all. Repairing is rarely worth the time or effort.