Basically how and what should I convert to change the Psion from the Expanded Psionics Handbook for 3.5 to be usable in Pathfinder?
Psionics have now been converted to Pathfinder rules officially via Psionics Unleashed from Dreamscarred Press. It was open play tested prior to publication so the rules seem pretty solid. I've been running a Psion (started at 1st at 5th now) and haven't run into anything weird.
It might be worth noting now that Dreamscarred has continued to support psionics with many additional releases. I got my Psion up to level 15. He was quite powerful in terms of ability to lay out raw damage. Can't speak so much for utility powers as I designed him as essentially an elemental energy carpet bomber.
\$\begingroup\$ thanks for the answer with experience! How is the power level compared to the other classes? \$\endgroup\$– C. RossJun 3, 2011 at 17:12
\$\begingroup\$ I haven't actually played (or played with) an arcane spellcaster in Pathfinder yet so I can't directly compare against them. At low levels he was less useful (but better then a 3.5 psion because PF adds some at-willish powers for Psions) but he's becoming capable of taking big groups down fast as long as he can determine what their worst save is. (Different energy types require different saves so pick their weak one and better chance of success.) I think in the long term he will outstrip the fighter and paladin but for now the entire party seems to pull their weight equally. \$\endgroup\$– mirv120Jun 3, 2011 at 18:11
It looks as though there are rules for Psionics on the Pathfinder SRD. I should note, however, that the content appears to be from a third-party publisher, so your mileage may vary.
8\$\begingroup\$ In this case, Dreamscarred Press is one of the best d20 System companies out there. Their quality is typically much higher than that of Paizo itself. \$\endgroup\$– KRyanDec 2, 2012 at 16:57
I'd provisionally just convert skills and the like; I don't think the Psion particularly needs additional powers, since it's not like it was especially weak in 3.5. If you think it does, a bonus feat progress is probably simplest. Depending on power selection, you may need to rebalance the powers themselves some, since a whole lot of spells got edited in Pathfinder.
\$\begingroup\$ Well I was thinking of limiting powers to only what's available in Expanded Psionics and not including Complete Psionics or any other supplemental material. I'll have to look through and see what is overpowered compared to comparable spells in the Pathfinder Rulebook. I was wondering if I should offer some psionic abilities to function like 0 level spells/cantrips do in pathfinder (ie they don't drain the power point supply) \$\endgroup\$– rleahcimFeb 16, 2011 at 16:16