Certain pet races are considered Mountable, this means you can ride them like for example riding a horse.
Tip: For a full list of the mountable races go to Library > Races > Mounts.
If you have a mountable pet, go to Minions > Manage then click on the Pet and click the Mount button (if you see Dismount it means you are already riding it).
When you mount a pet you may gain access to special mount buffs of which there are two varieties:
Some races have several manual spells, and you are permitted to have up to 3 mount spells active at any one time, however if you dismount the spells are automatically terminated.
As well as the mount spells you will find any mount provides a 20% boost to Maximum health, and a 5% boost to both spell and physical evasion skills.
Note: There are no penalties to using a mount, you do not need to dismount to fight.
Buying a Mount
Not all pets are mountable so when looking on the Marketeer make sure the pet you are about to buy is a mountable pet, to visit a Marketeer go to 31, 59 then click on the Marketeer NPC and click the Pets button.