I need to know how to write a 10*10 matrix of pixels immediately into Vram instead of copying byte or word by word

Also, I would be glad if someone told me how to think of a game like xonix
How to do filling algorithm on assembly

If you are in a graphics mode then often the video RAM is often mapped to address 0xa0000 as a simple linear buffer.

Depending upon the mode you might have one byte per pixel through the palette DAC, or two bytes RGB 5:65 or 5:5:5, or four bytes as RGB 8:8:8, or some other combination that produces colours from the byte values.