Activate Zameck Guildmage's first ability by paying {G}{U}, causing each creature you control to enter the battlefield with an additional +1/+1 counter this turn.
Activate Ashnod's Altar by sacrificing Grazing Kelpie, adding {C}{C}.
Grazing Kelpie dies, triggering its persist ability, returning it from your graveyard to the battlefield with no -1/-1 counters due to Zameck Guildmage.
Repeat from step 2.

Infinite colorless mana

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Zameck Guildmage

Grazing Kelpie

Ashnod's Altar

Activate Zameck Guildmage's first ability by paying {G}{U}, causing each creature you control to enter the battlefield with an additional +1/+1 counter this turn.
Activate Phyrexian Altar by sacrificing Grazing Kelpie, adding one mana of any color.
Grazing Kelpie dies, triggering its persist ability, returning it from your graveyard to the battlefield with no -1/-1 counters due to Zameck Guildmage.
Repeat from step 2.

Infinite colored mana

Phyrexian Altar

Combos with "Grazing Kelpie"