I think this is in Final Fantasy 8 too. Last time I check the dark matter teachs Quitis a special and can be refined into 100 Ultimas.

Yes it teachs Quistis her ultimate limit break and it also can be refined into 100 Ultimas. I never really bothered with Quistis so I never really cared to get it.

Yea You can get a good ability for Quistis, but 100 ultimas is really good, put it on elemental defense for 100% in all.

<font color=red face="comic sans ms">To get a Dark Matter, you need to refine 100 Curse Spikes using the ability Tool-RF. I think GF Siren has to be at level 100 for you to be able to do this. You can get Curse Spikes easily from Imps, Tri-Faces or Malboros. And the name of the limit break is Shockwave Pulsar, which can cause over 9999HP damage, but is not particularly damaging (compared to Squall's and Zell's limit breaks agyway) ;)