Well. Dark Crater is a hard dungeon especially with your type combination. However, you
should do well. If you have any X-Eye seeds, throw em at Darkrai, then move onto his
minions. They're your first priority. Ryperior is ground type, so you should take them
down first. If your Chimchar knows Dig or Agility, or some other useful attack such as
Overheat, be sure to make good use of it. The fire type pokemon on Darkrai's team will be
harmful to your Bulbasaur so avoid them if you can or use attacks - or seeds - that will
stun them or delay them long enough for you to strike. Also, use moves that aren't Gr***
type ( don't use Vine Whip, Leaf Storm etc. ) Once you take down his minions, go for
Darkrai. Make sure you have more than 1 X-Eye seed, they last a long time though not
forever. Be sure to keep him stunned and the battle will be a breeze.

i goot a strong picachu kill all lighting rod pokemon then use discharge hits all
oppnents

my Invernape wich is my partner is level 89!

use fire moves with chimchar and bring 20 reviver seeds and you will be fine

then u might beat him