FIRST QUESTION: Okay, I want to know how to make my entity explode on death. I have a vague idea of how it should work, and that it has something to do with events, but I have no experience in that at all.
SECOND QUESTION: Let me make myself very clear. I want mywarrior to hold/use a random array of custom weapons that I made. How can I do this?
To do something when an entity dies, override EntityLivingBase#onDeath.
To control which equipment an entity can spawn with, override EntityLiving#setEquipmentBasedOnDifficulty to set the random equipment (calling the super method if you want random armour). You then need to override EntityLiving#onInitialSpawn to call the super method and store the returned value, call EntityLiving#setEquipmentBasedOnDifficulty and EntityLiving#setEnchantmentBasedOnDifficulty and then return the value returned by the super method.
Look at vanilla entities to see examples of this.
Side note: 1.8.9 is outdated and probably won't be supported for much longer. Consider updating to 1.10.2/1.11.
Please don't PM me to ask for help or to join your mod development team. Asking your question in a public thread preserves it for people who are having the same problem in the future. I'm not interested in developing mods with people.