Lyxen
Great Old One
Dude. You keep avoiding. I laid out the summary of RAW facts. So I'll try again as questions for you to answer.
Speaking of avoidance, why don't you answer mine first, I believe it was asked before yours...
1. Can I by RAW, without having done anything else at all during a round, ready an action to crawl 15 away from the caster when he disappears?
You can ready a ''move up to your speed", this is RAW. Does this pose a problem to you ?
Now, about the crawl, no, you can't ready specifically a crawl. It might be that you are prone, although, honestly, if you are doing nothing apart from readying your action, the minimal action that your character should take is to stand up to be ready to dash away. Not doing is is purposefully disconnecting the description of your actions and the intended resolution. But even if you are prone and unable to get up, it still works, see below.
2. Will this readied action by RAW go off when the trigger completes(disappearance) before the thunder or reappearance of the caster?
Yes, by RAW. Does this cause a problem to you ? It does not for me, at all. Why ? Because, once more, although you (wrongly by RAW, as proven many times now) imagine that movement is uniform across the distance, this is not what the game says. the rules put limit on how much you can accomplish in terms of distance covered in a unit of time that is not fixed, since nothing describes the actual percentage of the 6 seconds round in which you are actually moving. Even if you cover only 30 feet, you might cover them at a leisurely walk while discussing, or you could scramble like a madman in an instant and spend the rest of the 6 seconds recovering from that mad scramble.
So even if you are prone when you ready your move, the DM would be perfectly justified in saying: "from the corner of your eye, you see the caster disappear, knowing that the boom is coming you lunge across the floor, scrambling, rolling desperately,... and you feel the thunder of the blast just brush you by why you lay panting, recovering, 20 feet away from where the caster was."
And now your turn:
- First, prove to me that the interpretation above in any way contradicts the RAW. It might violate YOUR sense of verisimilitude, but I'm sorry, it's not universal.
- Second, the problem with your vision is that the problem does not come at all from Thunder Step. It only crystallises here because you have decided (your rules, not the RAW) that appearance is simultaneous with disappearance and therefore occurs before the thunder, and that all that happens so fast that nothing can happen in between. Neither of these are said by the rules. The problem is you imagining the round as perfectly uniform with seconds ticking by and events that happen "in an instant" actually happening within 0 time, perfectly simultaneous. You would have exactly the same problem with someone pulling a lever to open a trap, if someone was prone, you would not allow him to crawl away fast enough even if he was ready for it. That's fine, it's part of your role as a DM to say what is possible or not in your game world. But what is not fine is you trying to impose that vision on others just because you feel like it and feel that the rules should support you in this. They don't, the game is way more open than that and in particular about creating a sense of narration that is truly heroic and in line with the genre, where such escape are routine.
That's it. Nothing else matters. Not whether the DM would make some sort of ruling(those aren't RAW and don't apply to RAW discussions). And not whether you could move in a different manner.
Actually they do, because I find it strange that you would punish a player for not teleporting more than 15 feet with his Thunder Step and not punish him even more for trying to screw up the system by making a description of what he is doing that makes no sense in terms of action loop. Basically, the player would both say that he is preparing to run away and at the same time not doing anything to be as ready as he can. I've never seen a player act like this, so it's purely theoretical on your part and therefore devoid of any practical value in this discussion.