You want make an ability to lay mine? How can the mine explosion?
First------------------
Go to the Item Abilities,find Item Place Goblin Land Mines,you can set the level and set it to Unit Ability,off the item ability.
Mine Explosion----------------------?
Go to Special Abilities,then click Units,it has an ability that name is AOE Damage Upon death,it use for goblin land mine which near the land mine will auto explosion,also you can add level and damages.
Sentry ward?--------------------------
It same with goblin ability,go Item Abilities and find the Sentry Wards (Item)
Statis Trap?-----------------
Same with anothers.