Jumping Onto Larger Enemies

[Saeviomagy]

I'd probably look to the 'underfoot' rogue power for how this sort of thing might work, only requiring an appropriate athletics or acrobatics check as a move action to maintain in addition to the other requirements.

Additionally I'd probably stick terrain powers onto specific monsters that are only activatable whilst riding the target in question.

 

[Turtlejay]

Alternatively, make it a quick time event!

Shout out easy math problems, and if the player can answer them in less than a second or two he succeeds at that action!

2+2! You roll under his legs
4+11! You leap on his back, stabbing your daggers into his flesh
3x6! You climb up to his face
14-5! You stab him in the brain, you win!

Seriously though, quicktime events usually suck, especially when it amounts to killing a 60 foot monster in a few seconds.

Jay

 

[Delgar]

Keep in mind that the more dice rolls you require for an action the more likely the action has a chance of failure and the less likely your PC's will "think outside the box"

Best to just keep it simple single roll and just add a description. Maybe give the player a bonus for being creative.

Just my 2 cents