As a whole, I can
- Decide how serious or down-to-earth you are,
- Arrange a trip for you, or even
- Pull your leg!
Remove the first three vital letters of me, and I am
- Dying of gloom and dullness,
- Solving puzzles in a shrine,
- Not the one making your blood red.
Now chop off my head, and I am
- A sea-dweller,
- Faster than anybody else,
- With a beginning but without an end.
So, what am I?
- The "chopping off head" is not done to the original word, but after "removing the three letters".
- Removing the three letters, all at once, gives something that satisfies all 3 properties listed in the 2nd section.
- I am new to this site (and also puzzling), so I welcome constructive criticism!