While common blue Keepas usually only yield 1-5 Arcstones at a time, Silver Keepas can yield up to 30 Arcstones (only when killed), and Golden Keepas up to 50 Arcstones (also only when killed), perhaps rarely even more.
Golden Keepas occur most often on the Corruption layer, so you might want to hunt for them there (take some corrupted Food with you, also a few Healing Beacons and some ladders), however the other two types of Keepas also can be found most often on this same layer deep underground.
When a Keepa of any kind is near, a symbol that resembles an Arcstone will start to blink and "pulsate" with blue circles coming from it on your compass.
If you tame Silver Keepas or Golden Keepas, feed them and harvest from them, you can usually only obtain 1-5 Arcstones with each harvest, different from their loot that they will drop when they are hunted and killed.
In former versions of Creativerse Arcstones could also be very rarely found in randomly spawning Wood Treasure Chests at night on the surface, but this is not the case any longer (as of April 2017).
Arcstones cannot be placed nor dragged into a quickslot nor directly into the world.
Arctek lights are not any brighter than the Gas Lamp, however their blueish light is rather unique. On the same space that arctek torches take up, player characters (and Creatures) can also go (which is the same for any kind of torches except Hidden Temple Torches), so these torches can be used to create air bubbles under water or light the way even in narrow corridors/mineshafts of only 1 block wide.
Arctek tables cannot be used as a storage and will not display anything either, but you can use them together with Placemats on top so it will look like your (up to 5) things are lying directly on the table.