The game will be structured into 4 tiers:

Mortal Kombat I
-Only the original 7 characters and stages are playable at this point
-Bosses: Goro and Shang Tsung (w/ old man skin)
-Once beaten with key characters, tournament II will open
(Eg. Liu Kang, Raiden, Sub Zero)

Mortal Kombat II
-Original 12 chars/stages + Kano and Sonya are playable
-Bosses: Kintaro and Shao Kahn
-Once beaten with key characters, tournament III will open
(Eg. Liu Kang, Kung Lao, Kitana)

Mortal Kombat III
-UMK3 cast/stages + Tourney II chars are playable
-Bosses Motaro and Shao Kahn (more powerful now)
-Once beaten with key characters, tournament IV will open
(Eg. Liu Kang, Raiden, Nightwolf)

Mortal Kombat Trilogy/Ultimate
-All chars from Tourneys I, II, III + all bosses to this point
-New chaotic versions of stage backgrounds
(Eg. Extreme weather, vortexes, earthquakes crumbling architecture)
-Bosses: A super charged Evil Raiden and The One Being