Forced Ride

As an alternative, a suitably large opponent can be treated as terrain for the purpose of jumping onto its back or clinging to a limb. After making any ability checks neccessary to get into position and on to larger creature, the smaller creature uses its action to make a ST or DEX check contested by the targert’s DEX check. If it wins the contest, the smaller creature successfully moves into the targets creature’s space and clings to its body

Forced Ride

LMoP Robotguy