A stubborn character does transfer the stubborn rule to the unit, unlike ITP, its very clear under the Character rules in the BRB (don't have it with me so can't give you an exact page number). This combo does work and its certainly an interesting build, saurus are amazing and with stubborn and immunity to fear from the Cold One Scar Vet they will be pretty much unbreakable as long as the BSB is in range. Cav is simply anything mounted on a horsie, cold one, wolf, boar or similar non-monstours cav sized mount, so I would assume this works (just like cav specific spells works on mounted chars).
The build has a few problems from a competative perspective tho;
1) 12" range means that you will be transfering it to max 3 units (including the one the carrier is in), and they are forced to stay within range.
2) You need to take a Slann or Old Blood with no other magic items as it costs 100 pts, which is not only expensive but also takes up all magic item points you have. This also means that you can't buy any protection for an Old Blood carrying it, making him very vurnarable to stuff like killing blow or multiple high S attacks.
3) Sure you have some stubborn saurus units but they are movement 4" and are easy to avoid. The CoC are very fragile and will die easily to shooting and magic. Its an extremly defensive build, and while it might work if you play a frendly game and you opponent just try to smash into the unbreakable saurus units a competative player won't be that stupid unless he has something with a TON of hit power.
The build also based on Saurus and Cold One Cav, which are usually not game winners. Most competative lists contain lots of stegs, magic, skinks, sallies and terradons, the Saurus Horde isn't exactly a tournament winner.
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