ok for a all about mercs post im sad . so ill give u butt load more on mercs .
1.they cost ya after level 10,you get charged every 15 min you have merc active it scales up at level 90 its like 100 plat every 15 min . so plan your ventures to earn ya enough plat to cover costs .setting mercs to passive when not using em will stop the charge after 2 cycles (30 min) which is same cost if u suspend a merc and bring it back up .. but still much cheaper then having to buy new after dismissing it by mistake

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2.merc race does matter large races dont get stunned .. can you say orge tank ..
3.dont wait to buy your merc .. the higher your level is the more the merc will cost you to buy, so if you buy it at level 1 its free you dont have to keep it out. you can level to 90 with out pulling it out once and when u do pop it; it will be level 90 .. saving you a whopping 10k !!
3.decide early. every time you want to buy a new merc it costs plats so decide your fav play style or what you need from your merc soon as possible lower levels cost less to buy if your switchin between tank and healer merc all time your droppin 10k a pop at lv90..
4. mercs follow pathin bugs just like npc so if your using pathing bugs your healer may be out of range at critical moment..
5. you dont have to have t4 merc to get t5 merc .. this is bunk herd lots ppl saying u have to do all the progressions to get t5 merc not true , each zone of the progression unlocks a merc tier you only need to do the warrens progression to get your t5 merc, granted if you do only warrens you char will only be flagged void b but you will be able to buy a t5 merc (tested still works may 24 2011) handy to have t5 merc when doing lower level zones too for your progression .
ps besure to vote on my posts i have bunch more goodies for eq pathing bugs , faction exploits exc ..