The reason these spiders are called Skulltulas is because they tend to have a human skull-shaped pattern covering their backside. They can range in size from small dog to holy-hell-it's-bigger-than-a-horse. One thing they all have in common though is a taste for human flesh, since they will ruthlessly attack Link whenever he's in the area.
In Ocarina of Time, there are a few varieties of Skulltula to encounter. These Skulltulas have an incredibly pronounced human skull pattern on their back, complete with gaping eye sockets and even a hole where the nose would go. It's almost as if someone glued a Halloween mask to their backs.
The largest breed of this spider is more massive than adult Link. It hangs from the ceiling and will drop down in a surprise attack once you get within range. After it has lowered down on its web, this Skulltula will execute a spin attack if Link gets too close while facing the spider's back (the easiest way to defeat it is to slash at its exposed belly).
Smaller varieties in this game are the Skullwalltula and Gold Skulltula. Skullwalltulas usually hang out in areas where Link has to climb, clinging to vines and rock walls. If Link gets too close, this spider will charge at him and knock him off the climbable surface.
Gold Skulltulas are more docile, but will still cause damage to Link if he touches it. Defeating this breed of spider will enable Link to help a family in Kakariko Village who were cursed and transformed into human-Skulltula hybrids (yes it's as horrifying as it sounds). As you collect Gold Skulltula tokens, the family members will turn back into humans one by one.
Skulltulas also make an appearance in The Legend of Zelda: Spirit Tracks. As Link travels the land in his train, there are certain sections of the map where these spiders will drop down and hang right over the tracks. They will proceed to swing back and forth over the tracks, making for a somewhat challenging target to hit with the train's cannon, especially when you're moving at top speed. Like their counterparts in Ocarina of Time, these Skulltulas are huge, easily as big as the train itself, and contain pretty much the same skull pattern on their backs.
In The Legend of Zelda: Twilight Princess, our favorite arachnids once again show up for combat, but in a form we aren't used to. Unlike the previous two games we just discussed, where this enemy primarily hangs from webs or climbs on walls, the Twilight Princess Skulltulas are capable of walking on the ground. This makes them a much more dangerous enemy since they aren't limited to staying in one small area like we're used to seeing.
|A Skulltula lowering onto the battlefield.|
Also the pattern on their backs is much less pronounced, appearing as if someone took some face paint and tried to draw a vague skull-like face on them. As a matter of fact, when I played through this game I didn't even recognize them as Skulltulas for a while because of these differences (when they walk on the ground it's actually kind of hard to even see the pattern on their backs).
That about wraps up our quick look at this shudder-inducing enemy in the Zelda games. Did any variant of Skulltula give you the creeps?