Well - let me cover some of the tactical sides of things.. I'm off today and putzing around vs bots atm to get familiar... its a bit odd.
1st - so you summon the void gate. The void gate has around 800-900 hp (eg can't be immediately destroyed). The gate lasts 150 if not destroyed. You can summon another gate at 150 seconds. Void gates are IMMUNE to skillshots and AOE spells - you've got to auto attack to destroy them. Cast range to setup the gate is small (eg pretty much on top of you).
Minions spawn from the gate every 4 seconds. Now, after 12 seconds, each void spawn now gains 50% of your mr/arm as damage (which is around 100 dmg with just the item itself + your built in stats). Void spawns attack MINIONS, TURRETS, and INHIBS. I'm not certain, but I don't believe champs get gold for killing void spawns. You also get all the gold generated by your void spawns if they last hit a minion. In order, void gates target minions, then turrets, then inhibs (currently a bug where they will try to attack a base turret even if inhibs are up and inhibs are in range to attack).
Their attacks between minions and turrets are different. Minions they just aa and do a little damage. To turrets they are like a small bomb. Just be aware that they can easily tank a turret shot or shots so they always get through unless weakened by a champ or minions.
Lastly - void gates have a limited range - once outside of the limited range, the voidspawn die very, very quickly. If placed right, you can setup a gate and it void spawn will be able to attack 2 turrets. That's about the max range though (can't describe super well - range is decent though).
OK - so how to use.
defensive ideas
- Position them to support you under turret - makes your turret more difficult to take as you constantly pushing out minions
- Position them further down the lane to slow a push or draw attention (eg my turret 1 is under attack, I drop this up near enemy turret 1 to take creep agro). This could be used to end/slow split pushes
- Just use as a distraction to ease pressure.
- use as a ward for top lane - kind of smeh idea, but you can see things around it and it could fit in a few places for safety and be useful too.
offensive
- If you are able to farm past a turret (ex think singed), dropping a void gate back where its safe means your voidspawn will be doing 100% damage to the turret. Voidspawn focus on minions if there are any first, so this allows for fast pushing on turrets. You also help the team because you almost certainly draw the jungler and/or mid as, not only are you an annoying putz, but you are also taking out a turret at the same time.
- Really, really, really useful on sieges. You can use them to slow a push in another lane while you siege. And honestly, that can be pretty big imo. They are also useful if placed directly near where you are sieging. They pack a bit of a wallop. even if only a few get through - that makes a difference in the siege.
Another thought - perhaps donger could use these out of top lane or even as the terrible support dong.