AI DraftFeb 26, 2026
Ashnod's Altar + The Great Henge
Overview
When you cast The Great Henge, the spell is first moved to the stack and its cost reduction is determined and locked in before you may activate mana abilities such as Ashnod's Altar; therefore activating Ashnod's Altar during the casting (to sacrifice a creature for mana) does not change the cost reduction for that casting. Ruling [2025-10-02]
Step 1
You announce you are casting The Great Henge and move it to the stack as the first step of casting the spell, which is governed by . Ruling [2025-10-02] notes that any change to greatest creature power caused by this step will be used for the cost reduction.
Step 2
At the casting step that determines the total cost, The Great Henge’s cost reduction ("This spell costs 
less to cast, where X is the greatest power among creatures you control") is calculated using the greatest power among creatures you control at that moment and then that total cost is locked in, per .
less to cast, where X is the greatest power among creatures you control") is calculated using the greatest power among creatures you control at that moment and then that total cost is locked in, per .Step 3
After the total cost is determined and locked in, you get the chance to activate mana abilities to generate mana before paying that locked-in cost, under . Ashnod's Altar is a mana-producing activated ability you may activate at that time (it requires sacrificing a creature as part of its activation).
Step 4
Sacrificing a creature to Ashnod's Altar as part of activating it happens after the cost has been locked in, so that sacrifice cannot retroactively change The Great Henge’s already-determined cost reduction (see and the example in ).
Step 5
You then pay the locked-in cost (using any mana you produced, including from Ashnod’s Altar) and finish casting. If you wanted the sacrifice to affect the cost reduction, you must sacrifice the creature before beginning to cast The Great Henge so the greatest power at is different.
Resolution
You cannot change The Great Henge’s cost reduction by activating Ashnod’s Altar while casting The Great Henge. The Great Henge’s cost reduction is determined and locked in at the casting steps described in and , and you may only activate mana abilities (like Ashnod’s Altar) after that determination under . Ruling [2025-10-02] makes this explicit.
Feedback