hi i have tryed it out and on my server it works:
(item (name 2905)(Index 10000)(Image "item146")(desc 206)(class general refresh)(code 4 8 0 0)(country 0 1 2)(use 1) (plural 1)(cooltime 2000)(buy 0)(sell 3000)(specialty (buff 25 1800)))
(buff 25 1800)
the reason why this works is u tryed this
the null is the problem because i think 0 is the g of a buff or the power and u cannot increase a buff of a everytime crit...