Malcolm, Keen-Eyed Navigator + Magmaw + Amoeboid Changeling + Worldwalker Helm

Malcolm, Keen-Eyed Navigator

Magmaw

Amoeboid Changeling

Worldwalker Helm

How it works

1. Activate Amoeboid Changeling by tapping it, causing Magmaw to gain all creature types until end of turn.
2. Activate Magmaw by paying 1 and sacrificing another nonland permanent, dealing 1 damage to an opponent.
3. Malcolm triggers, creating a Map and a Treasure token.
4. Activate a Treasure by tapping and sacrificing it, adding 1.
5. Repeat from step 2.

This loop relies on turning Magmaw into a Pirate using Amoeboid Changeling's ability so that its sacrifice damage triggers Malcolm, Keen-Eyed Navigator. Every time Magmaw deals damage to an opponent this way, Malcolm generates a Treasure token, which Worldwalker Helm replaces and amplifies into an additional Map token. You can then sacrifice these newly created artifacts to pay Magmaw's activation cost, turning your entire artifact supply into an endless stream of direct damage.