They can be found randomly in castle or town keeps throughout the land, trying to raise support for their cause. The claimants will never be found within the borders of the faction for which they are the claimant. Talking to a traveller and paying a small fee will give you the current location of any claimant.
Siding with a ClaimantEdit
Once you find a claimant, they will tell you their side of the story and will ask you to take up their cause. If you have less than 200 renown, they will tell you that you need to gain more. With over 200 renown, the claimant will allow you to swear an oath of vassalage and your allegiance changes to the rebel faction. If you were starting your own kingdom, you have to give up your kingdom to become a vassal of the claimant. If you belonged to the faction that the claimant is trying to overthrow, the fiefs you currently own convert to the rebel faction of your claimant (temporarily under your control).
The other side of the coinEdit
Talking to the current leaders of each faction, you can ask for their side of the story. Both the Claimant and the current leader have good reason for supporting their right to rule. Generally, the current sovereigns justify their right to rule with practical arguments (such as that the kingdom is better off under their rule), while the claimants justify their right to rule based on law or technicality (such as where their lineage places them in the traditional line of succession to the throne). It is never stated in-game who should be the rightful ruler of each faction - it is up to the player to decide.
Victory with a ClaimantEdit
Once you eliminate the original faction, your rebel faction becomes the "original" faction and you become the marshall of the new king or queen (permanently in classic; you can step down, but it can never be taken from you).
In Warband, you also lose all the abilities associated with being a ruler such as assigning fiefs or sending emissaries. For this reason, beware of turning companions into lords during a claimant quest as they do not remain 'yours' when the original faction is defeated. Rather, they become lords of the new "original" faction led by the new monarch. If you'd like to have a companion as a prisoner, it may be easier to give them over during a claimant quest than force them to rebel during your own bid for kingship.
Classic and Warband ClaimantsEdit
|Dustum Khan||Lethwin Far-Seeker||Lord Kastor of Veluca|
|Lady Isolla of Suno||Prince Valdym the Bastard||Arwa the Pearled One|
With Fire & Sword ClaimantsEdit
|Ivan Barabash||Mehmed Giray||Stepan Razin|
|Janusz Radziwill||Former Queen Christina|