For Hangul, Hiragana and Katakana we are using the following replacement fonts:

Arial_18 :      Dodum 15        *)
Arial_22 :      Dodum 17        *)
CourierNew_18:  Gulim Che 15
DebugFont :     Gulim 15

All of them contain the following charcter ranges:
0x000000 - 0x0000FF Latin + Latin Supplement
0x001100 - 0x0011FF Hangul Jamo
0x0020A0 - 0x0020CF Currency Symbols
0x002190 - 0x0021FF Arrows
0x002600 - 0x0026FF Misc Symbols
0x003040 - 0x0030FF Hiragana + Katakana
0x003130 - 0x0031FF Hangul Compatiblity Jamo
0x00AC00 - 0x00D7FF Hangul

*)
Additional ranges:
0x000100 - 0x0001FF Latin Extended A + B
0x003000 - 0x00303F CJK Symbols and Punctuation
0x004E00 - 0x0050FF CJK Unified Ideographs

Note: In general almost all fonts are incomplete and therefore miss specific characters, even if the range is covered.