This is an effect that is gained from only two pieces of armor:
- Wyrm Mail
- Wyrm Mail +1
There has always been a lot of mystery as to what exactly this trait does. Bronto has written a wonderful description of his experimentation with this trait that was originally posted on Allakhazam.com:
I was very fortunate to receive this just last weekend. When I returned from Dynamis, I went to immediately do some experimentation. For the testing, I went into Rolanberry Fields using the bats, bees, goblins, weapons, and morbols as my guinea pigs. I also made sure to unequip my weapon, and let my wyvern do all the tanking/attacking. I experimented with Warrior, White Mage, Samurai, and Monk support jobs.
First of all, support job "abilities" are not granted. Nothing was added to pet commands. Your wyvern isn't going to provoke a monster off of you, or steal a pretty little coin. It also won't divine seal it's healing breath. The description of the armor is poor - abilities and traits are extremely different.
/WAR: It took a while to notice anything. When I first equipped the Wyrm Mail, my wyvern was doing 4 damage than normal. I assumed attack bonus was affecting him. However, I also recently attained level 75, so I was not sure if the armor or level was affecting his hitting. I did some equipping/unequipping, to sort of "reset" the support job trait granted to your wyvern. After some time, he finally double-attacked.
/WHM: Thinking the equipping/unequipping factor may "change" the random trait granted, I equipped the Drachen Brais for +10% Wyvern HP, and waited. After equipping the Wyrm Mail at three different times, Auto-Regen had been granted to my wyvern every time. This made me wonder if a certain sub granted a constant trait.
/MNK: Sounds peculiar, but this was the most important, and somewhat disappointing fact-revealer. For this, I equipped the Wyrm Mail -after- I summoned my wyvern, to see if Max HP Bonus would kick in, much like +10% Wyvern HP kicks in when you equip the Drachen Brais after your wyvern is already out. No dice - no Max HP increase. Right there it told me that you wyvern does not receive -all- support job traits - little bit of a downer, but any single trait to your wyvern is still pretty cool and fun. I fought a -lot- of targets, and my wyvern simply did not counter. I assumed Subtle-Blow kicked in.
I apologize for the length of my post. It seemed that there was still a lot of mystery behind the Wyrm Mail, so I decided to share my findings. I'm still having some fun testing some sub jobs, like /BST for some random killer effects and /RDM for the next-to-nowhere possibility that Fast Cast might make my wyvern execute healing breath with less "casting time". I'll just have to keep playing around.
Based on the info I've gathered thus far, it seems your wyvern does in fact receive ONE(1) -random- support job -trait-, and it seems to change-up when you re-equip the Wyrm Mail.
The abilities and appearance of the Wyrm Mail are quite rewarding. Good luck to all who search for it.
I've had the Wyrm Mail for a few weeks now, and experimentation I've done has made me suspect that ALL support job traits are added to your wyvern, but only if you're wearing the mail when you use the "Call Wyvern" ability.
/MNK - Wyvern HP is increased. I think in the above information, because Bronto had equipped the armour after calling his wyvern, he didn't get the effect. I've not noticed any Counter effects, but I rarely get Counter when I'm MNK main so it could just be me.
/RDM - well, Fast Cast would be nice, but my RDM is too low to be a useful sub so I've never used it.
/WAR - Double Attack on your wyvern is one of the greatest things you get from this bit of gear. Increases your damage by a load, and it seems to trigger about as often as it does for me as DRG/WAR. Attack Bonus adds to this too.
/SAM - This is probably the easiest one to prove, using <pettp> it's obvious that the wyvern has Store TP, and Zanshin means he strikes again when he miss a lot. So my wyvern definitely gets at least two job traits from the Wyrm Mail.
Another note, you don't need to wear the armour the whole time to get the effects - just have it on when you Call Wyvern. After that, you can switch back to your normal gear.
I've recently come to realise that your wyvern loses the support job traits if you zone. So if you plan on fighting with these effects, make sure you equip Wyrm Mail and Call Wyvern every time you change area.
I realise a lot of what I've written is available elsewhere, but not on here - I can confirm that these points are true though, and if you're on Phoenix, I'll show you.