Sigh.... Force of Nature/ Lord of the Pits

[LotusHead]

Force of Nature says you MUST pay GGGG or else...
Lord of the Pits says you MUST sacrifice a creature or else...

My knowledge from back when tapped blockers dealt no damage said that the Force'e upkeep thing was optional because it asked for a mana payment, whereas the Lord of the Pit demanded a sacrifice and blood must be shed if possible.

The question, is Lord of the Pits's upkeep terms mandatory if you have another creature in play, while the Force of Nature's upkeep terms completely optional? Assume the game was at stake and an appropriate Circle of Protection was availiable each time.

(Playing against a casual kid with a kick ass Elf deck that only my Moxen can deal with most of the time.)

[SimpleHiker]

Lord of the Pit - Update
"At the beginning of your upkeep, sacrifice a creature other than Lord of the Pit. If you can't, Lord of the Pit deals 7 damage to you. 7/7"
The card tells you you must sacrifice, you have to. There is no choice here.

Force of Nature - Update
"At the beginning of your upkeep, Force of Nature deals 8 damage to you unless you pay GGGG ."
The wording here says its optional upkeep cost.

You can download the oracle online or just search wizards for the card.

SH