muddy terrain question

Create a level 1...8 Spirit. For all creatures within its range, all creatures move 10% slower than normal and speed boosts have no effect. This Spirit dies after 30...78 seconds.

what about speed nerf like armor of earth?

I would assume "Speed boosts" is pretty specific.

But Then again..skills can have misleading effects.

Speed Reduction spells stack with muddy soil. Bringing people to a crawl... its very handy in GvG