How to Counter an Immobile Mage as an Assassin?

Do something early on to condition your lane opponent to react a certain way to certain actions.

For example, let's say you kill your opponent or at least chunk a good amount of health before they have all their item/skills to stop/mitigate your attack. If you can successfully do this several times, they should realize that if they don't throw out all their abilities you'll just blast them. Once you think you've got the enemy in this state, pretend like you're going in for something devastating.

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I get your point, but can you give me some examples of "something spooky"

I'll use an example with , my main.

Land a Q, and walk behind minions and pretend to try to ult her. She'll stay back, and you'll zone her. If you're lucky, she'll burn her CC (assuming you can dodge it). If they don't... well, denying farm wins you the lane as well as kills.

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I play Talon, and I would like to know about this a little further. So like, I e onto Lux and go behind her, she'll miss her q because of what you said? Does that mean that I don't even have to wait for her q to be used?

Yeah. If you start running towards Lux she'll possibly throw her Q out at you - if she does that and you E quickly enough, you'll appear behind her and the Q will just completely miss. She's then defenseless, and you can burst her very quickly.

In another scenario, the Lux might know you'll dodge her Q with E if she throws it too quickly, so she might wait for you to jump on her before she throws it. But it takes time for her to turn and fire Q, which is a slow projectile, and the snare doesn't actually stop you using any of your abilities, so you can use your full combo on her before she has a chance to defend herself. The only time to be careful of doing this is when the enemy Lux is doing very well and you're not, because in that case you probably won't be able to burst her quickly enough and she'll actually be able to combo you (assuming she landed her snare) before you kill her, possibly resulting in your death.

The other advantage of blinks like Talon is that in the laning phase, appearing behind the enemy laner can leave them with no escape route. Obviously they'll want to walk under their tower so that you can't follow them any further, but a Talon E will put him directly between the mage and the tower, meaning that if they want to walk under their tower they have no choice but to walk past him. That is just free auto attack damage you're getting off.

I play mostly champions like Zyra and Syndra who (like Lux) are reliant for linear skillshots for self-peel, and assassins who can easily change their position are a nightmare for them because their peel just gets so unreliable.