Yea theres a few days you can do this, go to abilities and press CTRL+F then type channel, if it takes u to possesion then do it again. You come to the ability 'Channel' now edit the fields to whatever, change the options to visible, and if you want it automatic where your standing then change target type to Instant, or point/unit then edit the Area of Effect (Targeting reticule size). Change the Follow Through Time to 5 seconds, and art duration will make any art you have (except icons) loop. Now for the triggered part (Where the explosions and damage and sound will take place)...
Create a new trigger labeled Self-Destruct:
Event: Unit begins casting an ability
Conditions: Ability being cast equal to Self-Destruct (Channel)
Actions:
•Floating Text - Create floating text that reads 5 above (Casting Unit) with Z offset 0.00, using font size 7
•Set (SelfDestruct) = (Last created floating text) [Make it floating text]
•Wait 1 game-time second
•Sound - Play [laughing sound here] at (position of casting unit)
•Floating Text - Change text of (SelfDestruct) to 4 with font size 7.5
•Wait 1 game-time second
•Floating Text - Change text of (SelfDestruct) to 3 with font size 8
•Wait 1 game-time second
•Floating Text - Change text of (SelfDestruct) to 2 with font size 9
•Wait 1 game-time second
•Floating Text - Change text of (SelfDestruct) to 1 with font size 10
•Floating Text - Destroy (SelfDestruct)
•Unit - Explode (Casting Unit)
•SpecialEffect - Create a special effect at (Position of Casting Unit) using the model [Art explosion here]
•Set (SelfDestructBoom) = (Last created special effect)
•Wait 5 game time seconds
•Destroy (SelfDestructBoom)
To get the sound you go to sound editor, find the sound you want, right click on it and select "play as sound" (Or whatever it is that puts it in the right box)
That should make your guy laugh as he is channeling it... if you want it so you can cancle it (Suggested) make a new trigger with the event Unit stops casting an ability, then make it change a boolean variable (Like StillCasting as the name), after each wait check if stillcasting is false, if true then do the normal stuff, else do •Destroy (SelfDestruct[the floating text]) •Skip remaining actions
NOTE: This is all off the top of my head, and the font size gets bigger just for fun... i think theres a color option for floating text so u can make it get darker and darker red too...