The Boggle creature has an action that can lay down a sticky oil that covers the ground in the Boggle's space. In the DMG(p272) there are rules to Tumble, which lets you move through the enemy space once if you succeed.
Using them together could the Boggle use it's Oil Puddle during it's movement through their space?
The actions work out at least
Tumble and Overrun can be attempted as an action or bonus action so the Boggle could Bonus Action tumble, win the contested check and move through the space, still having its Action available to do the Oil Puddle.
That part is fairly clear. But... the Tumble and Overrun description say:
If the tumbler wins the contest, it can move through the hostile creature's space once this turn.
That implies that the space being moved through is NOT the Boggle's space to control and therefore Oil Puddle can't be used.
That's RAW anyway, of course DM fiat and rule of cool can easily affect that.
