Let's pretend you did that, and you, being a wise individual who has recently seen the light that is Everblight, is interested in using this as the nucleus of an army.
You're probably wondering a few things:
1) What do I do with what I just got?
2) I want someone other than Lylyth1. Who?
3) I LIKES IT! How do I get to 35?
What Do I With What I Now Own?
To recap, you are now the proud owner of the following -
-4x Shredders [4*2 = 8]
5 Blighted Ogrun Warspears 
Total: 21 points
In lieu of a full-on tactica for each piece, I'm going to offer highlights. There are plenty of in-depth tactical articles out there, to be honest, and this is a higher-level view.
What's Lylyth Do?
She's fairly simple - she's got an ARM debuff (Parasite) that's nasty, a workable anti-infantry spell that punishes the enemy for clustering around a hard target (Eruption of Spines) and a hilarious, if situational, way to shut down warbeasts with Bad Blood. And her feat is a free additional dice, so anyone that can boost to hit can roll 4d6 to hit. High DEF, what?
Her FURY5 doesn't come into play with spellcasting because if she can shoot it (and she has Eyeless Sight, so she pretty much always can draw a bead) she can hit it with a spell. Oh, and that also lets her beasties charge for free, which is nice on FURY5, trust me. Oh, and you can use her Bushwhack ability to shoot, then move, so you can mark a target for the beasties THEN get outta threat range.
ProsMobile (SPD7, pathfinder, bushwhack)
High DEF (16, can use Tenacity to get to 17 base, and access concealment w/o speed, LOS penalty)
Accurate spells (hit it with a RAT7 base on top of Eyeless Sight)
ConsSquishy (ARM14 base, 15 boxes. Doesn't take hits well at all)
Low FURY (potential liability with melee beasts, hard to run them up to full. Somewhat offset by fury-related rules on the bow)
NO defenses in melee other than eating a free strike
What's my Carnivean Do?
Short answer? Punch the crap out of things and buff its ARM. On the charge (especially when benefiting from Witch Mark) you're looking at a spray (not too accurate, but free) a boosted PS18 bite, a pair of PS16 punches, then four more PS18 bites. It's not the most accurate beast with MAT6/RAT4, but against most heavies if it can get the charge you're gonna be ok.
While Lylyth can help out with Parasite, remember that off the bat this is your only innate heavy-hitter. You want to not lose this guy. He's probably got a target over his head, too, as your only heavy for now.
ARM buffing (bonus to attrition against enemy beasts/jacks; they eat d3 every time they punch you)
Swift (SPD6 pathfinder, aw yeah)
Assault on the spray allows for fun targeting vectors/long threat ranges
ConsLow threat range on charge (9.5" to punch someone is...eh.)
ARM is so-so without Spiny Growth (which is 2 fury)
Somewhat expensive at 11 points, but you get what you pay for.
I've got a more in-depth article on this guy available, as well.
In short, they're cheap, guided missiles with a sweet animus. They're 2pts a head for a reason, but you've got four of them. Tenacity is very useful for the buff itself (+1DEF/+1ARM is almost always nice) and as a beneficial way of using excess fury off Lylyth, OR making sure you've got enough in the field. They're probably either moving into position (running or going Rabid for +2SPD and Pathfinder), or going Rabid (which is good for boosts on attack/damage) and either charging or walking up and biting.
Easy transfer target
Good at nomming infantry/softening up lower-ARM targets
ConsEasy to run up a lot of fury with four of 'em
Melee beasts on a warlock w/ small control area
On the bright side, these guys will teach you a bit about fury management, as in "What do I do when I have more fury than I can leech?" The answer is either 'write them off' or 'put them where they'll frenzy on an enemy.'
In all honesty, the Blighted Ogrun get compared to the Gatorman Posse. A lot. Often, it's not favorable. I'm going to focus on how to get the most out of them, because you basically got them for free over a normal battle box.
What these guys do well is take up space. They can threaten a fairly solid distance (on the assault, they're jogging up 8" and whipping a spear another 8" for a 16" threat range) and make people think hard about getting in range. Also, with Set Defense, they can make charges a bit more tricky since they're DEF14 instead of DEF12 against that charge, and the other guy probably wanted that extra dice since these guys are ARM16 with 8 health.
If you want them to kill a heavy, they'll probably want Parasite on it. On the bright side, on feat turn with the charge these guys can crank out a LOT of attacks. With Set Defense, they're not a bad front line, and Reach on their melee weapons means it's hard to skirt them.
Nice volume of attacks on the charge
Reasonably obnoxious to charge
ConsNeed charge to get plenty of attacks
Not Gatorman Posse
So, how does this all work together?
Lylyth will probably want to lead with the Warmongers; a couple out in front to make it hard to get to the ones in back. They're good for absorbing a charge, leaving your beasts to counter-charge. Basically, you want to keep that Carnivean alive, because if it implodes you're going to have a bad time trying for some assassinations. It's not impossible, but it's going to be a bit hard without his volume of attacks.
Lylyth basically picks something she wants dead, slaps it with Parasite, and then hits it with her army until it dies. Save the feat for a potential assassination run (with boosts on the attack, suddenly MAT6 is hyper-accurate with a nice 4d6 to hit...which should hit DEF20 about half the time. Which should be enough if it's the carnivean).
2) Lylyth is cool and all, but I want another warlock and then I want to expand
I'm going to discuss alternative warlocks first before I discuss expanding. We have a decent 21pt army that's faction-pure, so we'll keep that in mind. Running down the list...
Absylonia - Probably best to leave her out; she's more beast-centric and is unlikely to appreciate dropping 8 points on Ogrun, and I'd advise against a minimum-sized unit here.
Bethayne/Bayal - This is not necessarily a bad choice. Your current army setup doesn't really get much out of her feat, but the Ogrun could enjoy any of her three upkeeps, and if you're a Warmachine player you'll enjoy having an arc node (Bayal's her pet beastie and a channeler to boot).
Lylyth2 - Skip. She wants a ranged-heavy beast setup. You don't have that here.
Rhyas - She's an option if you want to add more infantry, as she's nice to run infantry and wants Rapport on one beastie for a MAT8/RAT6 heavy. She's workable; Legion has some solid infantry, but you're also likely to drop some of the shredders here. Not the most efficient use of your new goodies.
Saeryn - She makes people groan, and for good reason. The biggest argument against getting her is that her feat only protects her battlegroup, so those Ogrun are SO gonna die on feat turn. She also doesn't do a hell of a lot to support them, to be honest. Still, if you want to pick up another heavy and some fury support, she's an option.
Thagrosh1 - Honestly, I like this guy for an alt caster on the warpack. He's got a STR buff that the Carnivean or Warspears would like; it pushes the Carni up into stupid-nasty PS20-bite territory, and the Warspears go up to PS15 on both of their attacks. Fog of War helps everyone (hell, even the Carnivean can get up to DEF14 vs ranged) and makes the Warspears obnoxious as they're DEF14 (15 with tenacity) against a charge or against shooting. Also, he's got the fury (and Attuned Spirit) to hand out the animi and keep his upkeeps going.
Thagrosh2 - Not a bad choice either, here. Manifest Destiny buffs his not-inconsiderable battlegroup, and he's sitting on an ARM buff as well, which makes either his Warspears or Carnivean that much more obnoxious. Plus, he hits like a truck personally, and his feat is fun for either extending the threat range of his battlegroup, OR pulling them back to get another charge.
I can think of only a couple drawbacks - Large base + low DEF, and his beast points are piddly at 3, but he can spawn a lesser after he takes a hefty hit, so it's kinda like 5 points...
Vayl1 - She's more beast-centric than your initial buy is.
Vayl2 - Still more beast-centric than you are now, and frankly her tier is stupid-nasty. I have a hard time playing her outside of it, to be honest. There's nothing like a long-range armor-piercing charge that promptly retreats out of retaliation range.
Kallus - Workable, though in fairness he's a little more melee/infantry-centric than your setup. You could probably make him work, though Warmongers aren't an ideal choice.
Still 2) That's a lot of options. Narrow it down?
I would suggest Thagrosh1. If you're feeling adventurous, Thagrosh2. You have a solid infantry core and could play Thagrosh1's attrition game, especially factoring in Spiny Growth, Tenacity, and his -2STR aura. Thagrosh2 likes the shredders and can buff the ARM of your Ogrun to a healthy 18.
I feel like they're your best fits.
3) Ok, I get it. What am I buying next?
Lylyth desperately wants you to think about buying a Shepherd. Shepherds let you force outside of your control area, and also are good for pulling all the fury off a beast, or healing it outside of activation. Forsaken aren't bad either, though they can only hold 5 fury total (or a good couple turns of help) but CAN turn around and use that to punish anyone running high on fury or camping on focus.
I'd get at least one Shepherd first, maybe two. They're just solid. Consider one Forsaken as well, but they're more expensive and anyone that's been hit hard with Blight Shroud knows to target these things.
A Plastic Heavy Kit and MagnetsDo yourself a favor and buy a standard Legion heavy kit and magnets. You can magnetize the arms, and that way you have two bodies and you've a set of arms for a Ravagore, Scythean, and a pair of Carniveans. This is the most flexible way to go, honestly, and you probably want a second heavy.
Swamp GobbersThey're a point, they make clouds. Clouds provide concealment or block LOS. Buffing your DEF or blocking LOS to your warlock altogether are handy. These guys are just a solid, cheap utility piece.
Spell MartyrsThese guys are a 'maybe.' They're 1pt solos that are single-use arc nodes. Honestly, Thagrosh2 is the guy I'm thinking of first when I mention these, as a timely, accurate Scourge can be a game-winner because knocked-down casters are hard to miss. However, Thagrosh1 and Lylyth are both capable of appreciating an early-game Bad Blood on an opposing heavy.
Why not a Warchief?Now, some folks tend to reach for support solos that go with a unit or units, IE Banes and Bane Lord Tartarus. I'm not so sold on a Warchief with Warspears. He'll do precisely two things for them - let them heal after they kill something in melee via Blood Drinker, and IF he's in their LOS he'll buff their to-hit rolls. The issue is getting him in their LOS. Also, you're potentially tight on points and he's 3, fitting him and another heavy in there is going to be pushing it.
What Might My Army Look Like at 35 With This?
-4x Shredders [4*2=8]
5 Warspears 
Swamp Gobbers 
You keep your heavy hitter and little gribblies. Warspears go in front, potentially benefitting from the Gobber cloud. Ravagore lobs shots from a distance and suggests that the enemy come to you, and the Shepherd can happily sit back and manage its fury.
-4x Shredders [4*2 = 8]
5 Blighted Ogrun Warspears 
Swamp Gobbers 
I'm opting for a Scythean for its threat range - with Thagrosh1's feat letting you resurrect a heavy, you can happily start a piece trade with the Scythean (making it harder to kill via Spiny Growth and/or your -2STR CMD-range aura). Keeping Thagrosh behind the Ogrun screens him, and also lets them benefit from his -2STR aura. Carnivean and Shredders provide ARM/DEF buffs, and Fog of War stays up until you close in. If you brought gobbers, you can keep Thagrosh concealed without worrying about Fog of War; just drop that if the Warspears are going to make an assault attack.
Forsaken manages fury, and if anyone runs a warbeast hot to crack ARM, then it burns its fury and pops Blight Shroud and laughs at the messed-up enemy beast.
-4x Shredders [4*2=8]
5 Blighted Ogrun Warspears 
Swamp Gobbers 
Spell Martyr 
I've dropped the Carnivean for a Ravagore because I like the gun and wanted the support. The Scythean is a cheap beater, and in a pinch you can buff his ARM with Dragon's Blood and Tenacity if you need him to take a hit. Otherwise, Warspears get the ARM buff and lead. Ravagore makes the enemy think about closing, while the Swamp Gobbers and Tenacity make the enemy at least worry about DEF16 against shooting. Trust me, the biggest issue with Thagrosh2 is he's allergic to gunfire and hard to hide. Also, Spell Martyr + Scourge = hilarious.
Finally, there's nothing like the perfect long-range feat kill - cast Manifest Destiny for an additional dice to attack/damage rolls while discarding the lowest, get enemy caster into control range, pop feat. Shredders activate, go Rabid, and run at enemy caster. Then they move up and make a fully-boosted attack under the feat with Manifest Destiny helping. Or, just throw the Shredders 24" across the board (Rabid for a SPD8 run for 16", then a walk-n-chomp under feat...aw yeah. Poor Irusk dealt with that once. Survived the first run, had to deal with four about-to-frenzy shredders. Bad time for the reds, it was.).
You could probably make other casters work with the 2-player box setup, but I think the Thagroshes are probably your best bet for getting the most out of the box with common support. If you were to go to your friendly local gaming store and assuming you split the box for about $50, you'd be looking at about $40 for the support solos/units, and ~$45ish for the second heavy kit and magnets. Not bad, altogether, for a 35pt army with solid support.