Odyssey was about the time that Wizards of the
Coast started thinking of ways to make dual land
variants that played noticeably differently from
each other. In the case of the filter lands,
they will give you access to each color - but
they will always give you access to both
whether you want it or not. While other dual
land variants will help you with those
double-colored-mana costs, these ones work best
in decks that have slightly fewer colored mana
symbols, which are ironically the decks that can
sometimes work better without dual lands.
One thing that I've always found interesting
about them is that the "filter" activation cost
is colorless, meaning that you could in theory
use Mossfire Valley to splash red and green
cards into an otherwise mono-blue deck. This
level of flexibility is one that has rarely been
seen on anything short of the original dual
lands or Ravnica's shock lands, and has perhaps
decreased enthusiasm for a revisit and
completion of the cycle (not to me, though!).
Today's cards of the day are the filter lands
from Odyssey that require one colorless mana
then give two allied colored mana in return.
Aside from most likely not being useful in the
first turn and being unable to produce mana on
their own these are quite solid as an option for
many decks if supported with other mana sources.
The risk prevents them from being chosen for
most builds, but used in addition to another
duel land in a two color deck they can really
shine. Multiple sets aren't recommended
due to the increased chances of poor opening
hands, though single copies of more than one
type can still work well in Commander.
Whew, these haven't aged well at all. It's a
neat thought on fixing, but the new Filters have
taken the idea and run in an almost crazy by
comparison way. Though it's does the job for
those looking for fixing on a budget for EDH and