[Baalz]

Yes, as Cleavland says Lanka is one of the classic bless rush nations and configured for such they're going to have a strong advantage against most nations in this situation. That doesn't mean you can't win, but it does mean you're going to have to outplay your opponent to win because in straight fights few troops can wade in and defeat well blessed palankashas. In this type of situation you'll need to (temporarily) abandon your long term planning and go into full emergency mode, divert your mages and research from what you had in mind to short term useful stuff. Evocation and lightning are a good suggestion, here are a couple others assuming you're following the template in this guide.

Turn 15 you should have construction-4 done and a pretty decent gem income with your research surging. Palankashas have a small buckler and are vulnerable to sufficient archery, so one option would be to delay them a few turns and push up to construction-6 (you should be able to achieve this pretty quickly if you pull your pretender back for research duty and leverage those skull mentors you're cranking out), then leverage those dwarven hammers you've been building to crank out bows of war. Your Vanjarls have a base precision of 16 and can self buff aim, half a dozen of them firing from behind your PD (which being high defense glamoured will last longer than average) will be very punishing. Any one of these should also be able to destroy Lanka's monkey PD (which is very vulnerable to archery) and is stealthy and very maneuverable, so you should be able to take 3-4 of their provinces for each of yours you lose. Combine this with lantern shields, which will auto summon corpse candles to the flanks of your enemy, making them run around to deal with them while you punish them brutally. Mix in a couple of black bows, visions foes, piercers, just man's crosses for Lankas thugs and just generally to put more of your gems to use. Don't hesitate to recruit a bunch of indie commanders if you've got more bows than Vanjarls - though once you see how that 20+ precision works you'll be in love with using them.

Meanwhile you've pushed up to evocation-4, a quick run with your strong research engine. At this point you're dropping blade wind and thunderstrike, and you're officially past the part where you're under the gun of a "bless rush". Palankashas go down very quickly when you can bring this kind of artillery to bear.

Another option would be hitting the alteration research. Palankashas are going to be coming in relatively small numbers, dropping destruction on them is probably all it would take to make your huskarls very competitive - but as long as you're there use false fetters to serve them up on a platter.

So, again, no doubt you're gonna have a hard time dealing with a good Lanka bless rush, but by turn 15 your options should really start opening up. Trying to fight them with helherdlings is a sucker's game, you're playing where they have a strong advantage. Particularly if you're using a build like the one I suggest here - forget about your sacreds as you're not built to optimize them. Rather than do that, try to shift the fighting to where you can leverage the strengths that you've cultivated (strong early research, lots of early vanjarls, good early gem income).