Wisdom on Pyrithum killing?

The same way you beat down any good race. Kill them in pieces, or take away their strength. Pythium is particularly weak to assassinations, if you can get them through.

Cripple their economy; use things like Storms (by items or spells) to stop the use of so many javalins.

The problem with Pythium is they have no weak point so the longer you let them grow the better they get at everything.