At the beginning of your combat phase, Lagomos triggers, creating a creature token.
Deal combat damage using the creature that has Breath of Fury attached. Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the creature token, then causing you to untap all creatures you control and to get an additional combat phase after this one. 
Repeat each combat phase.

Infinite combat damage

Infinite combat phases

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite mana creatures you control can produce

Infinite creature sacrifice triggers

Infinite untap of creatures you control

Breath of Fury

Lagomos, Hand of Hatred

Activate Lagomos by tapping it, searching your library for Hostility and putting it into your hand.
Activate Mind over Matter by discarding Hostility, targeting Lagomos.
Hostility triggers, shuflling it from your graveyard into your library.
Resolve the Mind over Matter trigger, untapping Lagomos.
Repeat.

Infinite self-discard triggers

Mind Over Matter

Hostility

Activate Lagomos by tapping it, searching your library for Dread and putting it into your hand.
Activate Mind over Matter by discarding Dread, targeting Lagomos.
Dread triggers, shuflling it from your graveyard into your library.
Resolve the Mind over Matter trigger, untapping Lagomos.
Repeat.

Dread

Activate Lagomos by tapping it, searching your library for Guile and putting it into your hand.
Activate Mind over Matter by discarding Guile, targeting Lagomos.
Guile triggers, shuflling it from your graveyard into your library.
Resolve the Mind over Matter trigger, untapping Lagomos.
Repeat.

Guile

Activate Lagomos by tapping it, searching your library for Ulamog and putting it into your hand.
Activate Mind over Matter by discarding Ulamog, targeting Lagomos.
Ulamog triggers, shuflling your graveyard into your library.
Resolve the Mind over Matter trigger, untapping Lagomos.
Repeat.

Ulamog, the Infinite Gyre

Activate Lagomos by tapping it, searching your library for Kozilek and putting it into your hand.
Activate Mind over Matter by discarding Kozilek, targeting Lagomos.
Kozilek triggers, shuflling your graveyard into your library.
Resolve the Mind over Matter trigger, untapping Lagomos.
Repeat.

Combos with "Lagomos, Hand of Hatred"