Essence warps

This page describes how to modify the warps that occur after obtaining an essence.

Code for the essence object is located in object_code/common/interactions/essence.s#L341. The data which defines the warp destinations is in that file and looks as follows:

; Each row is warp data for getting an essence.
;   b0: wWarpDestGroup
;   b1: wWarpDestRoom
;   b2: wWarpDestPos
;   b3: wWarpTransition
@essenceWarps:
.ifdef ROM_AGES
.db $80, $8d, $26, TRANSITION_DEST_SET_RESPAWN
.db $81, $83, $25, TRANSITION_DEST_SET_RESPAWN
.db $80, $ba, $55, TRANSITION_DEST_SET_RESPAWN
.db $80, $03, $35, TRANSITION_DEST_X_SHIFTED
.db $80, $0a, $17, TRANSITION_DEST_SET_RESPAWN
.db $83, $0f, $16, TRANSITION_DEST_SET_RESPAWN
.db $82, $90, $45, TRANSITION_DEST_X_SHIFTED
.db $81, $5c, $15, TRANSITION_DEST_X_SHIFTED
.else
.db $80, $96, $44, TRANSITION_DEST_SET_RESPAWN
.db $80, $8d, $24, TRANSITION_DEST_SET_RESPAWN
.db $80, $60, $25, TRANSITION_DEST_SET_RESPAWN
.db $80, $1d, $13, TRANSITION_DEST_SET_RESPAWN
.db $80, $8a, $25, TRANSITION_DEST_SET_RESPAWN
.db $80, $00, $34, TRANSITION_DEST_SET_RESPAWN
.db $80, $d0, $34, TRANSITION_DEST_SET_RESPAWN
.db $81, $00, $33, TRANSITION_DEST_SET_RESPAWN
.endif

The first part is for Ages, while the second part (after the .else) is for Seasons. Each row corresponds to one dungeon. (Note that there is no entry for dungeon 0 / maku path, unlike with miniboss warps.)

Let's break down the first row for Ages, which is the warp data for the Spirit's Grave essence:

.db $80, $8d, $26, TRANSITION_DEST_SET_RESPAWN

.db stands for "define byte", which simply inserts a byte (or a list of bytes) into the ROM. So, all of the values here are byte values.

$80 Is the group number to send Link to. Actually, it's the group number with a bitwise OR of $80 applied to it. It's not obvious why this is, but it's not important - we can just ignore the first digit. So, value $80 means Link should be sent to group 0.

$8d is the room index to send Link to. So, combined with the group number, the full room index in LynnaLab is $08d.

$26 is the position Link should spawn at in the room. When the position is specified as a single byte like this, it always has format $YX, where Y and X are his position measured in tiles. So, $26 gives him Y-position $2 and X-position $6. This can be confirmed in LynnaLab.

Finally, TRANSITION_DEST_SET_RESPAWN is the transition type, as defined in constants/common/transitions.s. Typically it is TRANSITION_DEST_SET_RESPAWN. But in certain cases, when the doorway is not centered on a tile, the game also uses TRANSITION_DEST_X_SHIFTED, which places Link in between two tiles horizontally.