There are a lot of enemies in video games that come along and there doesn't really seem to be any sort of strategy that you can employ to avoid them and their absurd damage they dish out. There are some gamers out there that really enjoy this sort of "challenge" but I tend to think of it more as "cheese."
Some have almost unavoidable attacks, some have very small hitboxes, and other utilize aspects of AI that is damn near impossible for you to use on the level that the computer, with its millions of calculations per second and perfect (if the AI is set up that way) ability to counter anything you do with a level of accuracy that a human simply isn't capable of.
The High Templar in Starcraft 1 was one of the earliest gaming memories I have of an enemy that made me want to throw my computer out the window when I would encounter one.
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This little bastard didn't have much of a purpose for me when I was playing. I only used them on the missions that you were required to use them on and later I would only spawn them for the sake of getting Archons out of them. They are slow, they have no basic attack and if exposed, they are essentially cannon fodder because their only real purpose is to cast Psionic Storm, which is definitely the cheesiest attack that exists in the game IMO.
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While I am sure there are some very high level players out there that can effectively use this ability, I never found much purpose for it because if you get the High Templar close enough to an enemy group, they will spot you, and kill you very rapidly. The High Templar however, can be used very effectively by the computer's AI.
Whenever you are on the offensive, or even when creating units, you tend to bunch them together and put them in groups for the sake of an overwhelming assault. The computer is able to detect this and will send a rogue Templar out to Psionic Storm your ass and wipe out all of your hard earned units. For me, this was particularly annoying when siege tanks were set up in groups - which for me I had to do in order to avoid accidental splash damage on my own units. The computer would routinely, use a drop ship to sneak a templar in, cast Psionic Storm immediately upon hitting the ground, and wipe my siege tanks.
Of course this was a suicide mission on the part of the computer's unit, but at that point it doesn't matter. Now I have to produce all those damn siege tanks again only to have the process repeated by the computer again.
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I have never met a human opponent that was capable of utilizing this ability in such a fashion and while I am sure there are some Koreans out there that doing this is no problem for, but for me, I never saw much use for these units as an ally but I HATED them as an enemy. They can attack land and air units and the area of effect is rather massive.
I think the developers over at Blizzard were aware of the fact that this was going to annoy players and they actually built in a cheat code that would allow you to deactivate the computer's capability to use Psionic Storm. Of course this would also deactivate your ability to use it, but since I never used it effectively anyway, this was not a problem for me.
I consider all the Starcraft games to be some of the greatest titles ever made. To this day I can return to those games and play through all the missions again and even though I am already very familiar with the story, it is still entertaining.
However, I can still feel the rage that this particular unit brought into my life and I think this is just because I was incapable of countering it or even using the ability myself. Of course this doesn't make the game unwinnable, it just makes it take longer and kind of makes it extremely annoying.