0. Guide (primaris)
Guide has long been a staple Eldar power, and with this edition it's been improved dramatically: range went from 6" to 24", and it can now be cast on any allied model (not just Eldar). It's solid, reliable, and useful, whether you're running pure Eldar or taking allies for Tau or Dark Eldar. I don't really need to stress that twin-linking a units shooting is really good
It's worth noting that, unlike the Divination primaris power Prescience, Guide does not affect close combat. However, the 24" vs 12" range is a significant extension, as it allows the farseer to remain in a safe position even when your army is spread out.
|Nobody wants an autarch on the cover|
Three/two/one hits, with fleshbane, and you can pick the targets - Executioner certainly has the potential to be an excellent psychic. But the restrictive elements of the power - unreliable target selection and damage - mean that most of the time, the power will be disappointingly weak.
Executioner is a focussed witchfire, which means that you can only select its target(s) if you roll a 5 or less on your psychic test. On 2d6, you have a 5/18 chance of making that roll - slightly less than one-third. If you cast Executioner seven times during the course of the game, you'll probably get to choose who it hits twice. You have the potential to snipe out a chaos banner, special weapon, or sergeant with Executioner, granted, but your chance of doing so on any given attempt are pretty questionable.
Much like Guide, Doom is a solid, reliable, and enormously useful spell. It fills a similar role in the Eldar arsenal by amplifying the damage output of your army. This iteration of the power is especially potent because in addition to allowing re-rolls to-wound against an affected target, it can also be used on vehicles, letting your army re-roll armor penetration rolls instead.
Doom will be less effective against armies with lots of small units, but even in that situation it functions similarly to Guide. Its main downside is the the enemy can Deny the Witch, making Guide somewhat more reliable. However, where Guide will amplify the damage of one firing unit, Doom has the potential to boost the damage of several of your own units. Large terminator units, Necron wraiths, monstrous creatures, and similar high-priority targets that require an enormous amount of firepower to bring down are excellent targets for Doom. And by using Doom and multiple Guides, you can multiply your damage output to really ruin somebody's day.
|"Yer a wizard, Eldrad"|
3. Eldritch Storm
This psychic has seen a substantial power spike from the last Eldar codex, which is compensated for by its Warp Charge 2. You can't spin around vehicles anymore, but the power is moderately powerful and flexible.
While still S3, Eldritch Storm now has fleshbane and haywire. High toughness units are especially vulnerable, but a large blast that always wounds on a 2+ is dangerous against any target. The haywire rule makes the storm very effective against groups of vehicles, particularly vehicle squadrons. The hits will most likely be glancing, but having the option of softening up or finishing off a vehicle with Eldritch Storm makes it a very solid damage dealer.
Because it's dangerous against almost any target and has an excellent (for a witchfire) 24" range, rolling Eldritch Storm will almost always be useful. The double warp charge cost is problematic, but that's what your spirit stone is for.
Part Two Part Three