The crystal teleport seed
see that little red box i drew on this screen snap? the little thing in it?
that my friends is the Crystal Teleport Seed
paradoxically it has no gp value in the Grand Exchange, but is one of the most valuable items in game.
how you ask?
the Invention skill my dear readers.
the invention crafted item Crystal tool siphon (unlocked at level 54) sells for up to 1 million gp in the Grand Exchange. to make it you need the following components acquired by Disassembling items in game
Clear parts (common) - gained from disassembling glass items
Crystal Parts (common) - gained from disassembling crystal weapons, armor, tools, charged crystal teleport seeds, and harmonic dust
Imbuing Components (uncommon) -gained from disassembling battlestaves and wands
clear parts are slow and tedious. there is a buy limit on the glass lens for bullseye lanterns of 100 every 4 hours. and “empty lightbulbs” (which give 2x the rate of clear parts) are nontradeable and must be made yourself. so very slow getting them.
imbuing components... well if you buy and disassemble battlestaves you can recoup the cost by making Augmenters from the Powerful components they also give upon disassembling, but the initial cost is High.
crystal parts though... crystal tools, weapons, and armor are very expensive. And playing the harps in Prifddinas is very slow. You’re lucky to get enough dust for 10 crystal parts in an hour.
but Crystal teleport seeds.... ho boy.
during the quest chain to unlock Prif you get access to a little village called Lletya. there you find some Elves that can be killed. they tend to be weak to Crushing melee damage or fire magic damage, but really if you have high combat levels you can use any form of combat on them. they drop Crystal Teleport seeds very often.
set up and kill as many as you like. there is a bank near bye so no worries about picking up drops!
once you have a large amount of the tele seeds, charge them up. Talk to the roving elves or if you have Prif access, go to the Ithell district and charge them there. after the first 5 or so charged seeds the cost of charging them drops to 400 gp each which is practically nothing as the other items the elves drop can easily make up the amount.
then just bank them all, and pull them out as a Noted stack item. then disassemble them all.
before long you will have enough crystal parts for 10 or more crystal siphons which sell for 800k - 1.1 million each in the ge. (as of 10/25/2017 the ge price was 1 million each)