Still have a Strength of the Gladiator left over from yesterday. If I collect today's will I be allowed to have 2 or is there a limit ? Can I collect as many as I want ?
No. You cannot have two at a time; however, you can wait to use your first one until the second one is generated so that you can have two in back to back attacks (strategy for future alliance wars if incorporated).
Mine remains until I use it. I've had one ready to use and one waiting to be collected. Had this for several hours then used them fairly close to each other. Not sure why yours disappeared.
