CR adjustments on a mount

[Mystery Man]

Busily putting my adventure together for this weekend. Is there a CR adjusment for being mounted? Say, a frost giant riding a mastodon for instance...

 

[Crothian]

it would be the same CR, but you'd also have the second CR from the mount thus increasing the EL.

 

[Ridley's Cohort]

What Crothian said.

If the Frost Giant in question is notably effective riding that mastodon, it is only because he spent precious Feats and skill points to do so. Therefore it is a fair tactical payoff for the investment.

This tactic is also in "double jeopardy". Drop a Confusion spell on this team and they are hosed if either one of them fails the save.

This is just one of those encounters where dumb luck can kill a PC or two if they are foolish enough to stand toe-to-toe with everything they meet. I salivate to think what kind of damage a lucky critical with a huge lance can do. If our heroes are at least 7th or 8th level they should have tactics for dealing with this kind of encounter (or they deserve what they get).

 

[Slobber Monster]

Another approach you can take if you don't want the EL to be higher than the CR of the opponent is to figure the value of the mount as gear. (Mostly only applies to opponents with PC class levels). For example, a fully trained griffon costs 8500 GP, so you could give that to an NPC fighter and downgrade his armor from +3 to masterwork.