PC controls & hotkeys

C Character · I or V Inventory · K Expansion · J Jewel Bank
A Skill tree (master level) · P Party · G Guild · B Gens · H Events
X X Shop · D Commands · M Teleport list · O Options
Tab Map guide: zoom with - / +, list of NPCs and monster zones, click a name and your hero walks there (Esc stops).
Z MU Helper settings · Home start / stop MU Helper
U Window menu — every window with its key, if you forget one.
Esc game menu (exit, change hero or server) · F12 hide the game to the system tray

Left click walk, attack, talk to an NPC, pick up an item. Right click use the selected skill.
Hold the left button on empty ground: the hero walks where the mouse points and stops when you let go.
1–0 choose a skill. To put a skill on a number, open the skill list, point at the skill and press Ctrl + number.
Q W E R use the potion on that key. To set it, point at a potion in the inventory and press Ctrl + Q/W/E/R.
Space pick up the nearest item. End auto attack on/off with the selected skill ("END - Auto" shows).
L with the inventory open: repair mode. Alt + right click on a player: quick menu (trade, party and more).
Dark Lord: Shift + 1–4 commands for the raven.

Enter or a click on the chat box at the bottom left opens the chat, ready to type.
Click a player's name in the chat for the player menu (private message, online and device).

F10 free camera on/off. Then the mouse wheel zooms, the arrow keys and the middle mouse button turn it, F11 puts it back.

Game — walking with the held mouse, attacking players without Ctrl, names and HP bars, titles, item info on the ground.
Sound & Graphics — volume, graphics quality, text size and the FPS limit 60 / 144 / 240 (works at once).
Language — the game restarts in the new language and you stay logged in.
Screen — resolution and Window / Full screen, no restart needed.
Camera — height and distance sliders, remembered for every login, and Reset camera.

Every row in Options has a ? — point at it to see what it does and the recommended value.