Keeper + omen

[scarsabrex]

you tap the land for a color. that land is a forest mountain and plains. the text doesn't say mountain and or forest and or plains so multityped lands get extra value. so you get essentially 3 uses out of the keepers ability.

[Greg54js]

Oh right. Good catch. God I shouldn't be trying to answer rules questions when tired 

[BlackJester]

The trigger will only happen once. You'll get either:
{W}{W}
{U}{U}
{B}{B}
{R}{R}
Or
{G}{G}
Not four. If you tap a land, Keeper look to see if it was either a {Plains}, {Mountain}, or {Forest}. If the answer to any of these is yes, the trigger adds one more. If the answer is no, then it doesn't trigger. The same event (tapping a dualie) wont cause Keeper to trigger many times. It triggers once or not at all.

Sorry,
/hateratin'

[BlackJester]

^too slow

[Quackmaster5]

Damn! So it's not really a combo at all besides getting two for one. Crap! I thought I was on to something. Oh well. Still stunned the 💩 out of my friend when I had only five lands and played {last stand} to win the game. 😝 that woulda just been the icing on the cake to play that by using only a {leaden myr} and one land. 😝

[Poof]

Yup it says produced right in the wording.  When u tap a land for a mana, even if it can produce all types, it's still only producing the color you choose.  It didn't produce any of the others even though it could have.