Hello! I have a question regarding the Barrier and Smoke Cloud powers (although I suppose that can be extrapolated to all powers that generate some type of terrain). If my opponent has spawned smoke tokens with the Smoke Cloud power, can I spawn barrier tokens (using the Barrier power) right on top of one of those smoke tokens on my turn? If so, do I remove the smoke markers and put the barrier markers on top? Or do they both stay, one on top of the other? This question could also be asked in reverse, placing the smoke markers on top of the barrier markers.

Thank you!

You could place barrier markers on smoke cloud markers. You could not place smoke cloud markers on barrier markers, as barrier markers are blocking terrain.

The square would be the terrain type of whatever marker is on top, per the following:

Okay, thank you!

Wizkids actually answered this question 7 months ago.

BARRIER

Seven months ago was a different rule set. But they've left that up

So just to be clear, smoke cloud can be placed on anything other than blocking terrain?

As a side question can terrain markers be placed on anything but blocking?
And can you place terrain markers on two different elevations?

Debris Markers can be placed on Blocking terrain.

Effect Terrain must be placed at least 5 squares away from all starting areas during game set-up.

Blocking terrain markers cannot be be placed on elevated terrain markers because of how the Rule of Occupancy is interpreted.

No. Squares on different elevations aren't adjacent.

*Special terrains usually have a point cost, or are created by a vehicle being KOed. None are legal in Modern.

**I don't think there are any Modern legal maps with orange boundary lines. They have special effects that may or may not be tournament legal (the map will say)

Thanks for the answers!
So smoke cloud can be placed on anything but blocking then?

Generally under normal circumstances, except blocking and I believe the prohibition on excluded Special and Orange terrain would carry over from set-up into the game proper (it's physically not possible to place terrain markers on some special terrain).