Sigma Posting (Follow on BS)さんのイラストまとめ

Testamigma

Source: Testament
Guilty Gear XX (PS2) by Arc System Works

Oligma, Baeligma and Erigma

Source: Olaf, Baelog and Erik
The Lost Vikings (SNES) by Silicon & Synapse

Zigma

Source: Zim
SpongeBob SquarePants featuring Nicktoons: Globs of Doom (DS) by Natsume

Sigmanoa

Source: Klonoa
Klonoa: Door to Phantomile (PS) by Namco

Siginjigma

Source: Ginjirou
Guardian Heroes (Saturn) by Treasure

Nightmare Sigmero

Source: Nightmare Zero
Mega Man X6 (PS) by Capcom

Sigmaiden

Source: Raiden
Mega Man X4 (PS) by Capcom

Nightsigmare Virus

Source: Nightmare Virus
Mega Man X6 (PS) by Capcom

Sigroy

Source: Roy
Fire Emblem: The Binding Blade (GBA) by Intelligent Systems

Sigmilky

Source: Milky
Shock Troopers (Neo-Geo) by Saurus
Sigma face edited from sprites provided by @hansungkee1 and Aburtos