Underground River

(T: Add B.)

When this artifact enters, draw a card. 2: Add one mana of any color.

Prototype 1W — 2/2 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.) Vigilance 1, T: Put a +1/+1 counter on target Assembly-Worker you control.

T: Add C. T: Add B or G. This land deals 1 damage to you.

Mill five cards. You may put a permanent card from among the cards milled this way into your hand. (To mill a card, put the top card of your library into your graveyard.)

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Choose two — • Create a 2/2 colorless Construct artifact creature token. • Put a +1/+1 counter on a creature you control. It gains double strike until end of turn. • Search your library for a basic Plains card, reveal it, put it into your hand, then shuffle. • You gain 2 life and scry 2.

When this creature enters, mill three cards. You may put a land card from among the cards milled this way into your hand. If you don't, put a +1/+1 counter on this creature. (To mill a card, put the top card of your library into your graveyard.)