What can I do with my late game mana in Commander
I agree with the other answers, when the problem is "lots of mana, no spells to cast" the most obvious answer is "draw more spells somehow".

But I thought I'd take a look at the problem from a slightly different angle: if your deck consistently has more mana than spells to cast, maybe the problem is the deck's mana curve.

An ideal mana curve means you constantly have spells to cast, and the spells your draw and have in hand get more and more powerful as your mana base builds. Maybe your deck has too many cheap spells but not enough expensive threats?

But if you go too far, early in the game you don't have enough mana to play the spells in hand. However, there are many keywords in magic that help you "cheat" on your mana curve by increasing the power of your spells or increasing your card advantage when you spend a little extra. 

Keywords that help:


Cycling: Cast a big spell later, or ramp/replace the card early if you don't yet have the mana base.
Kicker/Multikicker, Replicate, Echo: Spend extra mana for a bigger effect.
Buyback: Easy way to get more spells? Don't put the cast spell in the graveyard. :)
Flashback, Retrace, Unearth: Another way to get more spells? After they hit your graveyard, cast them again.
Evoke: You can play something big later, or gain advantage early.
Forecast: You can play something big later, and gain advantage early.
Miracle: You can play something big later — or if you're lucky, sooner.
Suspend: You can play something big later or… uh… later.
Cumulative upkeep: Arctic Nishoba or Magmatic Core might be nice.
Level up: Make your board stronger.


I'm sure there are more… but that's a start.