You just completed the Everfall and nabbed your first Portcrystal, or it's your second playthrough and you want to make the world more user-friendly for Speed Runs or general gameplay. Fair enough, but be aware there are some limitations when it comes to placing Portcrystals. First, you can only place them in Gransys proper-you cannot put them in dungeons, towns... or pretty much any place that required a loading screen to reach. This excludes all of Bitterblack Isle, obviously. On the plus side, you can place them just outside of dungeons, for ease of access. Second, you are limited to placing ten Portcrystals around Gransys, not including the two freebies at Cassardis and Gran Soren. So, with that understood, here's a list (in order of importance) of the top ten Portcrystal placements, and why.
Put this one in the Greatwall Encampment, right outside of Greatwall.
This place is about as far as you can get from Gran Soren, and there are plenty of reasons to come here. First, for early-to-mid game characters there's the lure of the loot at Heavenspeak Fort and in the nearby Soulflayer Canyon. Second, a few escort quests have Greatwall as the destination. Third... it is again a long way from Gran Soren. You'd either have to go through the Estan Plains and Wilted Forest or the Deos Hills to reach Cursewood, and from there get around at least two Cyclopes and a Chimera to pass through Heavenspeak Fort, or go through the Soulflayer Canyon. Then, of course, there's the Barta Crags. Suffice to say it's as long and perilous a trip as any in the game. Quest-wise, you'll come here at the end of the game for a few missions, and you probably won't want to slog back and forth to Gran Soren during them. After encountering the Dragon, a Portcrystal here will let you easily access the Tainted Mountain Temple, which has the best loot in the game outside of the Everfall and Bitterblack Isle.
This Portcrystal goes right in front of the steps leading to Bluemoon Tower.
If it seemed from the previous description that the Barta Crags had the worst travel in the game... well, they're actually second to Pastona Caverns. To get here you'd need to go through the Deos Hills, then the notoriously obnoxious Northface Forest, replete with Chimeras, Griffins, Cyclopes, Direwolves, and Snow Harpies. After that, trudge through some winds and fight Skeleton Mages and Skeleton Knights, and of course the strongest Bandits in the game. There's also a Golem waiting along this route for you. Really, though, it's the Bandits that are the most dangerous here. The loot you'll skip with this Portcrystal in the Pastona Cavern is quite decent, but it's easier to reach just by backtracking from this Portcrystal location anyways. The reason this Portcrystal drop is secondary to the Barta Crags is simply because only two quests occur here, and both in Bluemoon Tower. No escort quests, and aside from one Notice Board Quest, there's no reason to really come back here late-game.
This Portcrystal belongs just outside of the entrance to the Shadow Fort.
This can be quite an bothersome trip from either Gran Soren or Cassardis, so why only 3rd? Well, once you clear the Ancient Quarry, it's not too difficult to reach the Shadow Fort on foot. Putting a Portcrystal here, however, saves you the trouble of crossing the Estan Plains, the Ancient Quarry, and the Hobgoblin and Saurian-infested Devilfire Grove. There are a number of escort missions that seek out the Shadow Fort, and two quests in the Shadow Fort; one story, one Notice Board. Otherwise, this Portcrystal allows you to access all of southern Gransys without having to run up the mountain pass near the Encampment. Granted, it's a far way off from the Witchwood, Aernst Castle, and Bloodwater Bay, but it's a start.
Stick this Portcrystal anywhere on the sandy shore of Bloodwater Beach.
Putting a Portcrystal solely for the numerous escort missions that have this desolate strip of sand as a goal. Even with the Devilfire Grove Portcrystal in place, it's an obnoxious, Goblinoid-infested journey to this bay. You'd have to skirt around a Drake and the Cyclopes near the Conqueror's Sanctuary, not to mention the Chimera that stalks the woods in between. Also, if you look at it, the distance between the Shadow Fort and Bloodwater Beach is about equal to that between Cassardis and Gran Soren... quite a journey. This also allows you to access the decent treasures along the beach, in the nearby mountains, and the bounteous fishing spots along the coast.
Put this Portcrystal along the road just outside (west of) Windbluff Tower.
This Portcrystal drop will allow you to skip the Deos Hills and get right to the Northface Forest. This is good spot for a Portcrystal, as it allows you to reach Windbluff Tower and Hillfigure Knoll easier, both of which you'll return to a few times throughout the game.
Place this Portcrystal just outside of the entrance to the Catacombs.
There's only one mandatory quest in the Catacombs, and all the other entrances closer to Gran Soren only give limited access to the place until after you go through it properly-through this entrance. It'll also put you closer to Soulflayer Canyon and Heavenspeak, in case you prefer this approach to the Barta Crags Portcrystal. Really, this Portcrystal is all about shortening Speed Run times, and making general playthroughs a little less bothersome.
This Portcrystal belongs on the bridge of the Mountain Waycastle, which connects Manamia Trail to Moonsbit Pass.
Again, another Speed Run Portcrystal. This one reduces the run time of a late-game quest to nil, and also puts you close to the Watergod's Altar, which has one quest within.
Place this Portcrystal near the Healing Spring north of the Blighted Manse.
Not an essential Portcrystal placement, but there are a good number of escort missions that go here. Also it gives you access to the Blighted Manse. Admittedly of limited interest, since only one optional quest takes place there. It's really all about avoiding the journey through the Northface Forest.
This Portcrystal wants a home just outside of the Witchwood.
Pretty much the Witchwood Portcrystal, who wants to run up those Wolf and Bandit-infested hills anyways? Witchwood has two important quests in it... although neither of them are mandatory. Also, this Portcrystal gives you fast-travel access to south-eastern Gransys, namely Aernst Castle.
Put this Portcrystal under the arch opening in the Abbey walls.
The least important Portcrystal drop, the only quests here involve Quina (who cares?), and it shortens the escort missions leading to the Prayer Falls (again, usually Quina, so who cares?) These escort missions were already pretty tame, so long as you traveled by day, stuck to the road, and didn't have the bad fortune to encounter a Griffin. Note that this last Portcrystal hub wasn't possible in the original game, where Cassardis didn't have its own static Portcrystal, and hence, needed one placed along Seabreeze Trail.