Tobias Forge / Papa Emeritus performs guitars on most Ghost songs

The following is the full list of credits available on Reddit.

Infestissumam

infestissumam
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass

Per Aspera ad Inferi
Simon Soderberg - gitarrarr, arrangements, programming and production, Mauro Rubino - keyboards, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Secular Haze
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Jigolo Have Megiddo
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Ghuleh / zombie Queen
Mauro Rubino - keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Year Zero
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Body and Blood
Mauro Rubino - keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Idolatrine
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Depth of Satan's Eyes
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Monstrance Clock
Mauro Rubino - Keyboards, Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Martin Persner - guitar, Rickard Stein (namechange from Rickard Ottosson) - bass, Tobias Forge - vocals

Meliora

Spirit
Henrik Palm - base and all the solo guitars, Tobias Forge - vocals and guitar, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

From the Pinnacle to the Pit
Simon Söderberg - rhythmguitar, Henrik Palm - bass and lead guitar, Tobias Forge - vocals, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

Cirice
Henrik Palm - bass, all acoustic guitars and all the solo guitars, Tobias Forge - singing and rhythmguitar, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

Spöksonat
Tobias Forge, Klas Åhlund

He Is
Simon Söderberg - guitar, Henrik Palm - bass, lead guitar and acoustic guitar, Tobias Forge - vocals and guitar, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

Mummy Dust
Simon Söderberg -guitar, Henrik Palm - bass, Tobias Forge - vocals, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

Majesty
Henrik Palm - bass and electric guitar, Ludvig Kennberg (studio) - drums, Tobias Forge - guitar and vocals, Klas Åhlund - Programming,

Devil Church
Henrik Palm - base and all guitars, Ludvig Kennberg (studio) - drums, Klas Åhlund - Programming,

Absolution
Simon Söderberg – rhythm guitar, Henrik Palm - bass and lead guitar, Klas Åhlund - Programming, Ludvig Kennberg (studio) - drums, Tobias Forge - vocals,

Deus in absentia
Simon Söderberg rhythm guitar, Henrik Palm - bass and lead guitar, Klas Åhlund - Programming, Ludvig Kennberg (studio) - drums, Tobias Forge - vocals,

Zenith (bonus track)
Simon Söderberg - guitar, Henrik Palm - bass, Klas Åhlund - Programming, Ludvig Kennberg (studio) - drums, Tobias Forge - vocals

Popestar (EP)

Square Hammer
Henrik Palm - bass, Martin Hjertstedt - drums, Tobias Forge - guitar and vocals, Tom Dalgety - producer and programming

Nocturnal Me
Henrik Palm - bass, Martin Hjertstedt - drums, Tobias Forge - guitar and vocals, Tom Dalgety - producer and programming

I believe
Tobias Forge - vocals, Tom Dalgety - producer and programming

Missionary Man 
Henrik Palm - bass, Martin Hjertstedt - drums, Tobias Forge - guitar and vocals, Fia Kempe (studio) - vocals, Tom Dalgety - producer and programming,

Bible
Henrik Palm - bass, Martin Hjertstedt - drums, Tobias Forge - guitar, Tom Dalgety - producer and programming,

If You Have Ghost (EP)

If You Have Ghosts
Simon Soderberg - guitar, bass, arrangements and programming, Aksel Holmgren - drums, Tobias Forge - guitar solo and vocals, Martin Persner - guitar,

I'm a marionette
Simon Soderberg - bass, arrangements, programming and production, Dave Grohl - production, drums and some guitar, Tobias Forge - guitar, vocals,

Crucified
Simon Soderberg - guitar, arrangements, programming and production, Aksel Holmgren - drums, Tobias Forge - bass and vocals, Martin Persner - guitar,

Waiting for the Night 
Simon Soderberg - bass, arrangements, programming and production, Dave Grohl - production, drums and some guitar, Tobias Forge - guitar and vocals,

Secular Haze - Live from the Music Hall of Williamsburg in New York City on 28 July 2013 
Tobias Forge - vocals, Simon Soderberg - guitar, Martin Persner - guitar, Linton Rubino - bass, Mauro Rubino - keyboards, Aksel Holmgren - drums,