A player in one of my campaigns has incredibly high initiative (+14) and also Step-Up and Strike. He is a Magus.
This is causing me huge headaches anytime I place a spellcaster enemy in the game. At the moment, the enemy usually gets one spell off at best before being assaulted and constantly followed by the magus and unable to continue to cast properly.
What's a good counter to this for me as GM?
Best Answer
Well, the guy has invested three feats to even get Step-Up and Strike, so it's good he's able to get some use out of it. But here are some (well, a lot of) counter-measures:
Best Option: Prevent the Magus from ever getting close
Simply design encounters such that the magus can't close with an important caster.
Design the environment so that there is literally no path to the caster; small rooms or narrow passages work well for this. So long as there are some minions between them, it'll be tricky for the magus to get up close. Encounters with different levels of elevation also work well at lower levels.
Cover prevents attacks of opportunity, even partial cover. So placing some strategic broken walls or flipped tables can provide the caster much needed shelter.
Some burly bodyguards who specialize in, say, trip attacks or grappling could simply grab onto the magus as he tries to close in, even if the path were otherwise clear.
Have the encounter start at a longer range; if they're out in an open field, the caster could get several spells off before the party's melee guys can close in
Conversely, have it start as a close range ambush. The bad guys have already prepared, and the magus's init doesn't help as much if he doesn't get to act in the surprise round.
Give the caster alternate movement; depending on the level, that could be flight, short range teleportation, or some means to pass directly through walls!
Attacks of opportunity can't be made against an enemy with total concealment. So an invisible caster doesn't need to worry about them; since you're at least a 6th level party, invisibility, darkness, and the like are definitely fair game for enemy casters.
Plan B: Once the magus closes
Have the caster take a move action back instead of a 5' step. The magus gets an AoO, but he'd get that anyway! And by the time the move is finished, they'll be far enough away to cast safely.
Let the caster simply make the concentration check to cast a spell without provoking. It's a tough check, but you could invest some of their feats and other resources into this.
As mentioned above, if they can gain cover or total concealment, there's no AoO for casting. Maybe a friend could do something as simple as pushing a turned over table between the two of them!
If one of their comrades steps in and grapples with the magus, he won't be able to follow you when you move away.
There are also tons of defensive spells that will help, such as mirror image.
Plan C