Activate Viscera Seer by sacrificing Rendclaw Trow.
When Rendclaw Trow dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Thran Vigil triggers, putting a +1/+1 counter on Rendclaw Trow.
Resolve the Viscera Seer ability.
Repeat.

Infinite ETB

Infinite LTB

Infinite death triggers

Infinite sacrifice triggers

Infinite scry 1

Viscera Seer

Rendclaw Trow

Thran Vigil

Activate Ashnod's Altar by sacrificing Rendclaw Trow.
When Rendclaw Trow dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Activate Ashnod's Altar by sacrificing Rendclaw Trow.
When Rendclaw Trow dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Repeat.

Infinite colorless mana

Mikaeus, the Unhallowed

Ashnod's Altar

Activate Viscera Seer by sacrificing Rendclaw Trow.
When Rendclaw Trow dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Vizier of Remedies.
Resolve the Viscera Seer ability
Repeat.

Vizier of Remedies

Activate Phyrexian Altar by sacrificing Rendclaw Trow, adding {B/G}.
When Rendclaw Trow dies, its persist ability triggers, returning it to the battlefield from your graveyard with a -1/-1 counter on it.
Activate Quillspike by paying {B/G} and removing the -1/-1 counter from Rendclaw Trow, giving Quillspike +3/+3 until end of turn.
Repeat.

Infinitely large creature until end of turn

Quillspike

Phyrexian Altar

Activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
When Rendclaw Trow dies, its persist ability and Necrosynthesis trigger.
Resolve the Rendclaw Trow trigger, returning it from your graveyard to the battlefield with a -1/-1 counter and a vigilance counter on it.
Resolve the Necrosynthesis trigger, putting a +1/+1 counter on Tayam.
Activate Tayam by paying {3}, removing a +1/+1 counter from Tayam, and both counters from Rendclaw Trow.
Holding priority, activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
Repeat steps 2-4 one additional time.
Activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
Resolve Tayam's ability from step 5, causing you to mill three cards and returning Rendclaw Trow from your graveyard to the battlefield.
Repeat.

Infinite +1/+1 counters on a creature

Infinite self-mill

Put a selection of permanant cards from your library and graveyard onto the battlefield

Tayam, Luminous Enigma

Necrosynthesis

Activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
When Rendclaw Trow dies, its persist ability and Sengir's first ability trigger.
Resolve the Rendclaw Trow trigger, returning it from your graveyard to the battlefield with a -1/-1 counter and a vigilance counter on it.
Resolve the Sengir trigger, putting two +1/+1 counters on Sengir.
Activate Tayam by paying {3}, removing a +1/+1 counter from Sengir, and both counters from Rendclaw Trow.
Holding priority, activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
Repeat steps 2-4 one additional time.
Activate Ashnod's Altar by sacrificing Rendclaw Trow, adding {C}{C}.
Resolve Tayam's ability from step 5, causing you to mill three cards and returning Rendclaw Trow from your graveyard to the battlefield.
Repeat.

Combos with "Rendclaw Trow"